Decouple Rift head tracking from avatar's head position

This makes the Rift's view reflect the user's physical movements exactly
while the avatar follows the movements as best it can.
added address bar dialog
Merge branch 'master' of https://github.com/highfidelity/hifi into 20061
Fix upright head model position calculation for avatar scale changes
Add finish lookup event
layout fix
use backslash to activate chat
Merge branch 'master' of https://github.com/highfidelity/hifi into 20061

Conflicts:
	interface/src/Menu.h
added go button active state icon
first cut at shape collisions
Merge branch 'master' of https://github.com/highfidelity/hifi into 20061
swith to using shape collider instead of spheres
make sphere entities use sphere shape for better collisions
Merge branch 'master' of https://github.com/highfidelity/hifi into moreWorkOnCollidingEntitites
make sure to scale default octree shape collision to meters
Merge branch 'master' of https://github.com/highfidelity/hifi into 20061
CR fixes
allow you to edit mass
Position Rift camera at avatar model's mid-eye location
Fix missing constructor initialization