GLMixer Code

BugFix: prevent changing aspect ratio when not appropriate (recording or
performance live mode) and fixed Session Switcher Widget (correct
behavior after loading file or changing dir).

Saving settings of dialogs

Fixed loading order & windows visibility

Improved saving settings of dialogs

Fixed and simplified source context menu

New Selection Manager, with simplified tags management and clean play
control toolbar. Removed control for smooth pause (to be implemented per
videofile instead).

Simplified and clean implementation of session switcher widget without
proxy view.

Implementation of performance mode for session switcher (with its load
of bugfix and improvements).

Project for snapping mechanisms in views

Change order of logs testing: prevents processing app events before init
og glmixer instance.