Two handed scaling should be more forgiving

[AndrewTHEManeri]

With certain shapes/sizes of objects, detecting the second hand is colliding with the object can be inconsistent. We should explore solutions to make this more reliable. Some kind of extra check such as the second controller ray hitting the object if the first is already pulling it around would probably be enough. Or maybe even as simple as the first time you do two handed scaling with an object, the second hand 'remembers' and will keep scaling when the trigger is down regardless of whether or not it is colliding with the object.

[mtschoen-unity]

I've gotten started on this in improvements/schoen/two-handed-rotate