Move navigation functions up into the driver object (now accessible from app)
Moved handleScroll navmode check inside handleScroll function
Factor navmode out of pointerLock implementation so navmodes can be app-specific
Improve the way that shift-click is handled onmouseup
Decrease scope of shiftDown variable to only inside canvas.onmousedown
Remove unnecessary parameter from appRequestsPointerLock
Factor pointerLock functionality out of satProperty
Merge pull request #217 from virtual-world-framework/make-navigation-overridable

Make navigation overridable