Bug 440289 - Combo Box in Editor 'Controls' inconsistent

- Changed the layout of the toolbar
- ToolItems converted to buttons
- ComboViewer is READ_ONLY again.
   
Change-Id: Ic3aff77b50b3475e4a3d63f824ffb8857aa5c018
Signed-off-by: Fabian Miehe <fabian.miehe@cassidian.com>