Схемы отсутствуют - Инструмент Twity Unity

Я понимаю, что это очень похоже на этот вопрос и этот, но ни один из ответов там не работал для меня. При попытке установить пакеты, упомянутые в этих вопросах, apt-get выдает следующее сообщение об ошибке:

Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 unity-webapps-service : Depends: webapp-container
E: Unable to correct problems, you have held broken packages.

Когда я пытаюсь установить упомянутые там зависимости, я просто нахожу все больше зависимостей. Synaptic Package Manager предоставляет сообщения об ошибках, когда я выбираю «Fix Broken Packages». Как это исправить?

Спасибо заранее, и прокомментируйте, если вам нужна дополнительная информация.

UPDATE: Запуск apt-cache policy webapp-container unity-webapps-service дал следующий результат:

webapp-container:
  Installed: (none)
  Candidate: 0.23+14.04.20140428-0ubuntu1
  Version table:
     0.23+14.04.20140428-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     0.23+14.04.20140414-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
unity-webapps-service:
  Installed: (none)
  Candidate: 2.5.0~+14.04.20140409-0ubuntu1
  Version table:
     2.5.0~+14.04.20140409-0ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status

UPDATE : Информация о версии:

LSB Version:    core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch:core-4.1-amd64:core-4.1-noarch:security-4.0-amd64:security-4.0-noarch:security-4.1-amd64:security-4.1-noarch
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.2 LTS
Release:    14.04
Codename:   trusty

ОБНОВЛЕНИЕ 3: При попытке установить unity-webapps-service используя aptitude вместо apt-get:

The following NEW packages will be installed:
  liboxideqt-qmlplugin{a} liboxideqtcore0{a} liboxideqtquick0{ab} 
  libqt5feedback5{a} libqt5multimedia5{ab} libqt5organizer5{ab} 
  libqt5positioning5{ab} libunity-webapps0{a} 
  qtdeclarative5-dialogs-plugin{ab} 
  qtdeclarative5-privatewidgets-plugin{ab} 
  qtdeclarative5-qtfeedback-plugin{a} 
  qtdeclarative5-ubuntu-ui-extras-browser-plugin{a} 
  qtdeclarative5-ubuntu-ui-toolkit-plugin{ab} unity-webapps-qml{a} 
  unity-webapps-service webapp-container{ab} webbrowser-app{ab} 
0 packages upgraded, 17 newly installed, 0 to remove and 0 not upgraded.
Need to get 26.6 MB of archives. After unpacking 103 MB will be used.
The following packages have unmet dependencies:
 webapp-container : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 libqt5organizer5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 qtdeclarative5-dialogs-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
                                 Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 webbrowser-app : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 qtdeclarative5-privatewidgets-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
 libqt5multimedia5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 libqt5positioning5 : Depends: qtbase-abi-5-2-1 which is a virtual package.
 liboxideqtquick0 : Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
 qtdeclarative5-ubuntu-ui-toolkit-plugin : Depends: qtbase-abi-5-2-1 which is a virtual package.
                                           Depends: qtdeclarative-abi-5-2-1 which is a virtual package.
The following actions will resolve these dependencies:

      Keep the following packages at their current version:           
1)      liboxideqt-qmlplugin [Not Installed]                          
2)      liboxideqtcore0 [Not Installed]                               
3)      liboxideqtquick0 [Not Installed]                              
4)      libqt5feedback5 [Not Installed]                               
5)      libqt5multimedia5 [Not Installed]                             
6)      libqt5organizer5 [Not Installed]                              
7)      libqt5positioning5 [Not Installed]                            
8)      libunity-webapps0 [Not Installed]                             
9)      qtdeclarative5-dialogs-plugin [Not Installed]                 
10)     qtdeclarative5-privatewidgets-plugin [Not Installed]          
11)     qtdeclarative5-qtfeedback-plugin [Not Installed]              
12)     qtdeclarative5-ubuntu-ui-extras-browser-plugin [Not Installed]
13)     qtdeclarative5-ubuntu-ui-toolkit-plugin [Not Installed]       
14)     unity-webapps-qml [Not Installed]                             
15)     unity-webapps-service [Not Installed]                         
16)     webapp-container [Not Installed]                              
17)     webbrowser-app [Not Installed]                                



Accept this solution? [Y/n/q/?]

UPDATE 3 : выход sudo apt-get install qtdeclarative-abi-5-2-1:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package qtdeclarative-abi-5-2-1 is a virtual package provided by:
  libqt5qml5 5.2.1-3ubuntu15.1 [Not candidate version]
  libqt5qml5 5.2.1-3ubuntu15 [Not candidate version]

E: Package 'qtdeclarative-abi-5-2-1' has no installation candidate

Выход sudo apt-get install unity-webapp-container:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package unity-webapp-container

UPDATE 5 : Выход apt-cache policy libqt5qml5:

libqt5qml5:
  Installed: 5.3.0-3ubuntu13~trusty1
  Candidate: 5.3.0-3ubuntu13~trusty1
  Version table:
 *** 5.3.0-3ubuntu13~trusty1 0
        500 http://ppa.launchpad.net/mscore-ubuntu/mscore-stable/ubuntu/ trusty/main amd64 Packages
        100 /var/lib/dpkg/status
     5.2.1-3ubuntu15.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
     5.2.1-3ubuntu15 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages

Вывод sudo apt-get install webapp-container:

Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies.
 webapp-container : Depends: qtdeclarative-abi-5-2-1
                    Depends: unity-webapps-qml but it is not going to be installed
                    Depends: webbrowser-app (= 0.23+14.04.20140428-0ubuntu1)
E: Unable to correct problems, you have held broken packages.