Fix issue #221 : Cycle through property pages with Ctrl+Return (forward) or Ctrl+Shift+Enter (backward)
Fix keyboard processing in various windows to make sure they don't hijack Ctrl or Alt keyboard combinations.

git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@350 c2f33eb2-41b2-391d-4cb4-d9d0608729ba