resources: remove unused images and icons

gen-resources.py should be used to generate resources.qrc and
JamiResources.qml. Steps to add an image resource:
- add the resource file to the appropriate path under resources/
- run gen-resources.py
- use the newly available resource

Note: only icons and images will be represented by Qml properties.

The resource file generation may be made to run during CMake
configuration in a subsequent commit.

Some unused components were also removed during the refactor.

Gitlab: #477
Change-Id: I8e7f13d465031666be2bbadd5f29f9afc94d210d