#16 Correction of trackball.py

[Anonymous]

This patch corrects bugs present in trackball.py making
it usable again.
It also implements renormalization of the quaternion
representation of
the trackball position every renorm updates. This
version is intended
to be used with tracking position of the mouse so for
zero rotation we
do nothing and for non-zero wi rotate further.

Pawel T. Jochym <Pawel.Jochym at ifj edu pl>

[Nobody/Anonymous]

Patch for trackball.py