PATH: post processor tweaks and loop select.

rename generic_post.py: This is actually a post specific to a machine.  The generic name is confusing
fix test case. Contour has no plunge angle
scrubbing postprocessors for python 2 style prints
Keep loop select usable when task panel is open.

src/Mod/Path/PathScripts/centroid_post.py

@@ -27,7 +27,6 @@ TOOLTIP=''' example post for Centroid CNC mill'''
 import FreeCAD
 import datetime
 now = datetime.datetime.now()
-import Path, PathScripts
 from PathScripts import PostUtils