settings: refactor for SettingsView - stage two

1. Remove redundant functions in AvAdapter
2. Add CurrentDevice for video device treatment
   Audio device treatment should be improved in the next
   stage
3. Add QSortFilterProxyModel to all video list models and
   manage them together to avoid redundant function calls
4. Video device call action should be responsive to device
   change as well

Gitlab: #508

Change-Id: I3df949a08bc19042b73f033139cd6ab06925c0b6