Add menu item that toggles VR display mode

Toggles the display mode if a Rift is found connected at program start.
Implementd sixense mouse emulation
Added menu options for sixense mouse input
Merge branch 'master' of https://github.com/highfidelity/hifi
Cleaned up a small bit of code
Move to previous line
Fixed build failure
Fix build warning in Audio.cpp

\interface\src\Audio.cpp(309): warning C4018: '<' : signed/unsigned mismatch
Merge pull request #3014 from Barnold1953/master

Sixense Mouse Input
Experimenting with ambidextrous sixense mouse input
Invert hydra move view and thrust controllers to match consoles
Merge branch 'master' of https://github.com/highfidelity/hifi
Store the last mouse move input type for application overlay
Merge pull request #3015 from ctrlaltdavid/build_warning_fix

Fix build warning in Audio.cpp
Support for multiple oculus overlay magnifiers
Removed left handed menu option
fix reference to attribute in STUN packet
Merge pull request #3017 from birarda/master

fix offset to attribute in STUN packet
Made applicationoverlay more readable
Fix for click and drag with sixense