skip unnecessary double-check of line collisions
moved "MODEL_TRANSFORMATIONS" from pycam.Geometry.Model to pycam.Geometry.Matrix (as "TRANSFORMATIONS")
fixed accidental reversion of contour model direction caused by some model transformations


git-svn-id: https://pycam.svn.sourceforge.net/svnroot/pycam/trunk@523 bbaffbd6-741e-11dd-a85d-61de82d9cad9