Terminate background worker threads on exit
First stab at approximate fixed-point math
Fast sin and cos based on lookup tables

Shaves some percent out of performance.
Remove unused Vector methods
Use fast cos in Vector.getProjectionOn()
Add code for fast arctangent based on lookup table
Use fast arctangent in vector length calculation

This is a big improvement - around 25% faster overall.
Minor cleanup
Exit all threads in case of mass extinction
Fix bug in fast arctangent calculation for third quadrant
Crank up precision of fast atan table to 1/100th of a degree