Fix ALLOW_OPTIONS
Fix ALLOW_OPTION precedence
Remove useless line

Maybe they meant 'ALLOW_OPTIONS = ALLOW_OPTIONS', in which case it would
actually do something, but we don't use it anyway so it's not an issue.
Disallow blank allow; set default to ALLOW_LEGACY
Improve constant names, values, and descriptions
Use if...elif... to make logic clearer
Fix range_detail
Fix the order of ALLOW_OPTIONS in forms
Reorder constants for aesthetic reasons
Sort the allow list in the Range detail view
Fix another test I broke
Fix range_detail again
Change max_length to 1; add schema migration
Merge pull request #282 from drkitty/range-allow-options-fix

Fix ALLOW_OPTIONS