GLMixer Code

Implementation of WORKSPACES in ViewRenderWidget and all views +
according changes in rendering of View interface.

Undo depth change and update of Undo / Redo action status (enabled/
disabled).

Undo manager support for new source, delete source and replace source.

BugFix: replace source reproduce alpha coordinates.

Protecting functions manipulating creation and suppression of sources in
the rendering manager and exposing to undo/redo only user-originated
actions of creation and suppresion (avoid recursive calls).

Implementation of Undo for creation / deletion of sources.

Bug Fix: fill_first_frame when stop using FirstFrameFiller.

Bug Fix: provide framerate for FreeFrame source.

Bug Fix: apply depth when loading FreeFrame source.

Recursive loopback: improved user preference.