Update issue #217 : Keyboard navigation between filters
Up/Down/Left/Right keys navigate the selected filter to the next filter in that direction
Keyboard shortcuts added for:
Properties - Enter or Alt-Enter
Context menu - Menu key or Ahift F10
Existing keyboard shortucts work on selected filter(s) - 
Delete - Del
Duplicate - Ctrl+D


git-svn-id: http://graph-studio-next.googlecode.com/svn/trunk@324 c2f33eb2-41b2-391d-4cb4-d9d0608729ba