improved collisions
Merge remote-tracking branch 'upstream/master'
Merge pull request #165 from Ventrella/master

improved collisions
Merge branch 'master' of https://github.com/worklist/hifi
GCC fails on these constants (ISO C++ forbids initialization of member
‘COLLISION_BALL_FORCE’), so I moved them into the CPP (they don't seem to
require external visibility anyway).