Changes:
- Accept setting an empty flags-type value in the settings tab
if the variable specification permits it
- Don't accept substrings of flag values
E.g. with values: 'one,two,three', 'hree', 'w', etc. used to
be accepted. Not any more
- Don't accept flags with random pattern-matching special characters
E.g. with values: 'one,two,three', 'on.', '(o)[n]e*' etc. used
to be accepted. Not any more.