Move Hydra movement code from C++ to JS

* removed Hydra C++ code from MyAvatar and Hand - closes #1916
* clean up lots of cruft
* added hydraMove.js
* added Cotroller.getSpatialControlRawRotation() to JS
* added several new Quat and Vec3 helpers to JS
* added setThrust(), getThrust(), and addThrust() to MyAvatar