Set amplitude calc back to original version.  Changed
setStrokeWidthAccordingly to make the brush output the actual volume
percent instead of a calculated width.  Curious to see how this acts on
the actual pressure pen.
improved pen detection upon plug in to headset jack.  Also added shake
to erase.
Added some extra test features like load image to draw on top of it and
save image, but the image isn't being resized yet, just testing some
things out.
Merge remote-tracking branch 'sardeenz/master'

Conflicts:
	Android/PressurePaint/src/com/option8/PressurePaint/PressurePenActivity.java
merging fork from sardeenz
Merge branch 'master' of https://github.com/option8/PressurePaint