Adding control over microphone sensing

Added an option for keeping the recorded media files instead of
overwriting them. Expanded microphone data to include the path to the
recorded audio file. Added a configuration parameter to control the
sampling rate.
Microphone code formatting & refactoring
adding petko to readme
Renaming Audio* to Microphone*
Adding support for keeping audio recordings
Adding support for keeping image files (via AbstractMediaSensor)
Refactoring config
Refactoring sensor-config default values
updating readme
More refactoring of config
Bug fix