Various fixes/enhancements

This adds the basic method to toggle flash in AVRecorder. 
I just added the TORCH and OFF modes cause those are the only ones that worked while recording video for my case. I'm not 100% sure if this is the proper way to support toggling of flash but it seems to work.

I also added a CameraOpenedEvent that will be sent to the EventBus whenever a camera is opened and will include the camera parameters with it.
This way any subscribers listening will get that the camera has been opened and can adjust their UI accordingly. For example If the camera opened changes a subscriber can re-check that the newly opened camera supports flash and if not maybe hide his flash-related-ui. 

Hope it's ok. Let me know if it needs changes. :)