Event Refactoring

- OUYAControllerANEEvent.as refactored to better reflect AS3 Events: properties passed as constructor arguments and made private with getters to prevent modification
- PlayerController.as simplified and updated to reflect event changes
- BUTTON_OUYA renamed BUTTON_SYSTEM to reflect guidelines (https://devs.ouya.tv/developers/docs/interface-guidelines), should probably consider making this more universal to use their official designations?