Feature/audio muxing

[israel-fl]

• Updated readme
• Updated how the EncoderConfig is initialized
• Removed some hungarian notation
• Added sample audio file
• Updated the way the encoders are released
• Added a ContentProvider for file exporting
• Added file authorities
• Added utility functions for file processing
• Added button for sharing video
• Updated EncoderConfig to have getters/setters

I think we can/should improve the initialization process. Mainly how the EncoderConfig is initialized, and how starting the FrameEncoder with/without audio is done.