Action: Slight clean up of the overview documentation.
Point class added
Point class test file added.
Types: Mostly whitespace and comment/documentation improvements.
Require clutter >= 1.12 because we now use ClutterPoint.
test/Makefile.am: Rename the new test to match its file name.

This avoids some confusion.
test-point-class: Some whitespace fixes.
Point: Replace the regularly-generated default constructor.

Because it creates a null underlying GObject, which is not what
people would expect, and which is hopefully not necessary.