Provide a WebVR device emulator

[delapuente]

It would be nice if we can provide a device emulator for the Unity editor emulating the behaviour of the template in the browser so development would be confined to Unity only,

[caseyyee]

@delapuente I think this commit fixes this issue? 205eb28

[delapuente]

This is for emulating the events happening in the browser. For instance, suppose we want to simulate we are switching off or disconnecting one of the controllers. This will happen on the WebVR side and handled in the browser resulting in some messages being dispatched to the C# code. In this emulator, we'd simulate sending those messages.

[caseyyee]

Gotcha. That makes sense.

[caseyyee]

Implemented as part of cross-platform support #306

Still need to support controller disconnects (as per your example), but at least they are handled in the same way now.