display options to help with 3d printing.

editmesh debug info,
- overhang (with axis angle options)
- wall thickness (with min/max distance)
- self-intersections.

access below 'Mesh Display' panel.


git-svn-id: https://svn.blender.org/svnroot/bf-blender/trunk/blender@56106 954f8c5b-7b00-dc11-b283-0030488c597c