Add in some more useful MonkeyRunner commands:

 - Add in device "drag" command to simulate a finger moving across the touch screen
 - Add in some pixel operation on MonkeyImage to scripts can do pixel level tests and comparisons.
 - Fix up the help command to no longer loop forever.
 - Start MonkeyRunner in interactive mode if no script file is specified.

Change-Id: Ifd2655d3291dcc9dc355d4c2efa9019dc38bee5d
12 files changed