Use .finish() to stop activity
Added documentation strings to all functions, see complete msg

* These documentation strings are really helpful to new people when browsing
  through the source
* In Android Studio you can use Ctrl-Q binding to see documentation of almost anything
  or use View -> Quick Documentation
* Some of them are still marked as TODO.
* Please fill them asap
* To create automatic documentations for functions, just type /** and hit enter in studio