Refactor user input bindings

[brianpeiris]

The user input system is in need of some refactoring (as of this writing @9223ec5)

• Most of the controllers (like vive-controller.js@9223ec5 use a round-about method of writing to the frame. They should just write directly to the frame, like the oculus go controller: https://github.com/mozilla/hubs/blob/9223ec59daa3ac4ae6d48437587be81dc8ddfd1c/src/systems/userinput/devices/oculus-go-controller.js#L13-L20
• Most of the devices use paths with dynamic methods, they should use static paths based on button and axes helper functions, like the windows mixed reality bindings: https://github.com/mozilla/hubs/blob/9223ec59daa3ac4ae6d48437587be81dc8ddfd1c/src/systems/userinput/paths.js#L246-L264
• The user input system ought to be unit-tested and is already isolated enough to do so directly in nodejs
• Perhaps less important, but it may be good to have the vive and oculus touch bindings use an implementation more like the windows mixed reality bindings, where bindings are split in to helper functions for re-use -- this is especially useful when the left and right controllers share certain bindings.

┆Issue is synchronized with this Jira Task

[johnshaughnessy]

bump. Still relevant