Handle one photo situation
Solved transition issue
refs #603
Fixed button menu scanning cycle count
refs #603
Removed trash import
refs #603
Fixed slideshow transition conflict
refs #603
Applied code review suggestion
refs #603
Merge branch 'master' into viewer-slideshow

Conflicts:
	pisak/launcher.py
	pisak/viewer/app.py
Merge branch 'viewer-loading' into viewer-slideshow

Conflicts:
	pisak/launcher.py
	pisak/viewer/app.py
Removed debug print
refs #620