Added redo icon to IconManager
Added component for keeping track of rendering setting changes
Added undo redo actions to rendering component
Render/Refresh after undo/redo action
Fixed a problem with alternating undo and redo actions
Just fixed some code formatting
Corrected some errors in the comments
Fixed some problems

- Don't clear history after saving
- Handle switch to grayscale/rgb
Another small fix
Fixed: Changes in inactive channels weren't stored in the rnd def history
Added checks for rndControl==null
Reset and use other user's settings was not applied to history
Fixed problem with multiple identical states added to the history
Merge pull request #2969 from dominikl/rendering_settings_undo_redo_2

Rendering settings Undo/Redo