Fix compilation old GCC version.
Fix libFreeFrame std string error.
Fixed Session Switcher transition (rendering glitch) and GUI appearance.
Fixed GUI appearance for combobox in Mixing toolbox
Clear settings in Mixing Toolbox. Standardized appearance of GUI.
Platform dependent Stylesheets for Qt GUI.
Make OSX app Retina compatible
Fixed Bundle OSX icon
OSX qrc
OSX bugfix Drag&drop
