Massive changes to orientations: use quaternions rather than Orientation
class.
Merge branch 'master' of https://github.com/worklist/hifi into reorient

Conflicts:
	interface/src/Avatar.cpp
Moved direction vectors to AvatarData, made them align with OpenGL view space
(to avoid the 180 degree rotations).
Moved gravity influence multiplier into constant, reduced.
Formatting.
More reformatting.
Offset camera fix, cleaner frustum transformation.
Merge pull request #466 from ey6es/reorient

Avatar orientation conversion: use quaternions rather than Orientation class, generalize rotations so that avatars can be reoriented based on gravity.
Save/restore the pitch and roll as well as the yaw.
Added --local option to avatar-mixer for testing.  Only update velocity,
acceleration, angular velocity, etc., for local avatar.
Merge pull request #468 from ey6es/master

Fixes for reorientation: load/save pitch/roll, don't update orientation for remote avatars.
Merge branch 'master' of https://github.com/worklist/hifi into 19351