Upgrading branch and repeat

Branch and repeat now both use expressions instead of fixed numbers. Far
more flexible!
Safer raytracer

The Wootracer now has some explict concurrency controls to ensure you
don't get re-entrant threads. Stop is also blocking until all threads
have finished.
New tutorial scripts

Lots of ready made scripts to get people started
New readme

v0.94 prep text
New installer (v0.94)

Ready to go with updated installer