Removing a magic number and collapsing two identical variables that hard-code the number of hands.
Remove debug cruft.
Removing unecessary #include.
fix copy-paste typo in comment
Fixing elasticity to range [0,1] during collisions.
close issue #1602 (particles overlap during collisions)
Added menu options for more detailed collision preferences.
added initial avatar-avatar collision stub
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction

Conflicts:
	interface/src/avatar/Hand.cpp
	interface/src/avatar/Hand.h
	libraries/particles/src/ParticleCollisionSystem.cpp
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction
Add particle-based bird
merge fix
Merge branch 'master' of https://github.com/worklist/hifi
Merge branch 'master' of ssh://github.com/highfidelity/hifi into avatar-interaction

Conflicts:
	interface/src/avatar/Avatar.cpp
	libraries/particles/src/ParticleCollisionSystem.cpp
	libraries/shared/src/CollisionInfo.h
Fixing iteration through list of avatars.
Removing build warning about out-of-order initialization in class ctor.
Splitting avatar collision check in two: vs hands and vs skeleton.