PEP8: Remove trailing whitespaces
refs #644
PEP8: E101 indentation contains mixed spaces and tabs
refs #644
PEP8: E225 missing whitespace around operator
refs #644
PEP8: E221 multiple spaces before operator
refs #644
PEP8: E231 missing whitespace
refs #644
Merge master into pep8
Merge branch 'master' into pep8
add opacity to image for MxButton
refs #632
Added ScanningException and its use
refs #673
Merge branch 'master' of ssh://git.braintech.pl/pisak
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
Fix line break
refs #673
Merge branch 'master' into pager-scan

Conflicts:
	pisak/viewer/app.py