Blender Git Loki

-> Vertex support for knife tool

Previously the knife tool only allowed you to cut through edges. This
approach is limited however, since many times you want to cut through
vertices in order to create precise cuts or terminate a cut in a specific
way. Blenders knife tool now supports cutting through vertices as
demonstrated in these pictures:

http://briggs.zanqdo.com/newknife1.jpg
http://briggs.zanqdo.com/newknife2.jpg

Since the vertex intersection code is very precise, vertex snapping has
been added to the knife tool to assist the user when they wish to cut
through vertices and can be toggled by pressing and holding the 'alt' key.

Notes:
-Vertex cutting and vertex snapping are only available when using the
'knife exact' option.
-Added various fixes to the precision of the knife tool.