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.