Adds target-selection list to set-creation-dialog; this also checks if at least one target was selected to be added to new set and complains if not.
Merge branch 'feature_add_backup_set' into 0.0.4. Adds a selection list to select the target(s) to be added to the backup-set-creation dialog.

Conflicts:
	modeling/recapp.asta
	production/done_today.txt
	production/schedule.txt
	src/bs/config.py
Fixes a minor regression bug in Signal.