GVR Event system needs some work

[WazzaMo]

Summary: The OnPointerEnter, Exit, Hover and Click events do not perform as one would expect and the event system is built in such a way that gestures cannot easily be defined.

Found using:

• Google VR SDK version: 1.130.1
• Unity version: 2018.1
• Phone manufacturer, model, and O/S version: Google Pixel
• Viewer manufacturer & model: Google Daydream (v1 I guess)

Steps to reproduce the issue:

1. Remove the controller pointer and instead set the DemoInputManager Controller Pointer to the GvrReticlePointer (I want gaze pointing)
2. Use HelloVR example and attempt to hook into the OnPointerEnter and Exit events with each handler logging out to Debug console.
3. Observe just how few events are generated for enter & exit (1 enter, no exits) despite the number of times you point at any object in the scene or move the pointer around.
4. Try other mechanisms such a building a class that extends the Reticle Pointer and overriding the event methods - only OnPointerHover() gets called with any frequency regardless of how many objects you look at.

Workarounds: There are none. It's borked

Additional comments: The API is difficult to extend due to the use of inheritance instead of has-a composition. For what is basically a raycast mechanism, this is overly complicated. I'm going to have to write my own.

[ddrocco]

Thanks for reporting, we'll look into this.