Added GestureAdapter, getters and enable-methods.

-FEATURE: Added a GestureAdapter convenience class.
-FEATURE: Added getters for all variables.
-FEATURE: Added enableGrab and enablePinch.
-OTHER: Changed the default value for the time between two gestures of
the same type to 750ms.
-OTHER: Updated the JavaDoc for several methods and classes.
-OTHER: Added a warning to readFrame(Frame), that it can miss gestures
if it's called too infrequently.
-BUG: circleStopped was not called if the gesture ended before the "time
between gestures" passed.