Add sensible default manipulators for 2D interaction.

I got this patch from the bug tracker, where Zach Mullen had attached
it.  The point is to provide some basic manipulators when in 2D viewing
mode.  The bug is here:  http://paraview.org/Bug/view.php?id=14171

Change-Id: I5c87223ead2e6539f28c3981cbe83d4722702062
Merge topic 'add-zachs-sensible-default-2d-manipulators' into next

2fa810c Add sensible default manipulators for 2D interaction.