Replace triangulation algorithm with CGAL triangulate_faces, the quality of generated mesh improved a lot.
This commit also reduced max uv packer times.
Add a crc64 hash check for history keeping to avoid repeated snapshot.
Besides, before, there is a logic error in the undo implementation, which recover the most recent snapshot from undo stack, so user need undo twice and at the second undo get the expected result. This incorrect behavior got fixed.
Jeremy Hu