adds an "add" button to the backup-set menu
adds comprehensive pep8 clean-up pass project-wide
Adds dialog window that prompts for details when adding set through menu in sets view. Dialog window also performs simple validation.
The "add" button now fully adds a backup-set, on the gui- as well as ctrl-level.
Bugfix: backup-set-gui is now unloaded correctly when loaded and its corresponding set deleted. Crashed before due to emptying canvas completely (through empty_canvas instead of close_set (on canvas gui), including arrow carrier); also empties canvas only if deleted set is the currently loaded one.
Backup-Set add dialog now responds to validation errors with a message popup specifying the exact error.
Adds small update to schedule
Merge branch 'feature_add_backup_set' into 0.0.4

Conflicts:
	production/schedule.txt