Fix typo in exception message.
Fix crash when adding a STUB plModifier to a plSceneObject
Use plDebug, and don't need function pointers to also be references
More friendly pyTempVertex.Color accessor

Python and lots of artithmetic aren't fun, so let's present it as an
hsColor32 instead of a BGRA integer so that users don't have to do
bitshifts.
That's unnesecary...