GRC context menu fix/update

The first commit fixes block specific actions in the context menu in GRC. The DrawingArea looses focus on context menu activation which cases an unselect of all blocks. Before the new search was added the DrawingArea never got the focus in first place and this bug never occurred.

The Second commit simply rearranges the context menu items a bit (block properties to the bottom) and groups them using separators. On my machine those are not show but I guess it can't hurt to have them in there.