Cleaned up pisak Button
Implemented Scannable interface
Updated scanning module
refs #631 #632
Merge branch 'master' into extended-scanning

Conflicts:
	pisak/widgets.py

refs #631
Updated scanning module to use Scannable
Fixed pseudoclass name in StylableScannable
refs #632
change emitted signal from "activate" to "clicked" to work with new scanning
refs #632
add opacity to image for MxButton
refs #632
Merge branch 'master' into extended-scanning

Conflicts:
	pisak/scanning.py
	pisak/viewer/app.py
	pisak/widgets.py
Merge branch 'master' of ssh://git.nimitz.pl/pisak