x/y-amplitude, 2 new buttons, calibrate Joystick

+ amplitude of all 4 directions (in % from -100% to 100% per axis)
+ 2 special Buttons F and E
+ calibrate Joystick function
+ new examples
Merge pull request #1 from mmuecke/master

x/y-amplitude, 2 new buttons, calibrate Joystick