added .gitignore file
FretView: improved, two input modes, drawing

Improved FretView by introducing two input modes:
 - manual input mode, when user select position by touching the screen
 - audio input mode, which use FFT to recognize played note/pitch

The position(-s) played is/are visualized, the position touched is visualized, the phases
of the pitch detection with FFT are visualized (squares under fret image). The listeners
on the FretView are informed about notes inputed, either as sound or manually.