RandomAccessIterator for TriangleMesh

~FIX: MathUtils now compares lessThan without using HP_EPSILON
 because otherwise it would violate the transitivity of the operator.
 (Same for other operators, except for areNearlyEquals(...))

~FIX: TriangleVerticeRefs now can deal with NULL-Vectors

~CHANGE: buildKdTree now uses it's own set of triangles, instead of
 the one iterated with _RandomAccessIterator.

+ADD: InvoluteGear test method.