Modify Input Event Pattern

[adamRenny]

Input should communicate to the Scene through observer pattern and wrap the original event within the HitEvent to support #60.

Requirements:

• Update observer pattern of the scene to listen to input directly
• Update HitEvent to encapsulate original event
• Provide HitEvent preventDefault method
• Decouple EventBus
• Remove namespaces in favor of observer/observable pattern

Merged tickets: #60, #58

[adamRenny]

Refactored out in c0767cfc59440400c31b5a938367f7895bc08026