Dev/poco input events

[StephenHodgson]

XRTK - Mixed Reality Toolkit Change Request

Overview

Several requests have been made to provide a way to consume input events in POCO classes and services. This gives a way to do that, but with some warnings:

• This should NOT be used in MonoBehaviour classes.
• Events cannot be consumed. eventData.Used would not apply here.
• There's no way to properly route events to subscribers in any specific order which may or may not cause race conditions in implementations that use it.

Target of the change:

Is this enhancement for:

• Core (core framework, interfaces and definitions)

Breaking Changes:

Are there any breaking changes included in this change that would prevent or cause issue for existing projects.

• Added Action<BaseInputEventData> OnInputEvent to the IMixedRealityInputSystem