Iss18 fqan handling

Resolves issue #18.

- The only case that now leads to the whole FQAN being inserted into the VO field is if the FQAN doesn't begin with a `/` (or, oddly, if the second half of the function raises an exception, but I don't want to mess with that). Before, other cases were if the FQAN did not contain "Role" or if "Role" was at the start of the string, but these are now removed as we should be able to accept FQANs without Role defined (short FQANs).
- The 'role' return value of the `parse_fqan` function now defaults to `'None'` if "Role" is not defined (rather than `'Role=NULL'` as this is only for when that is actually specified in the FQAN).
- Tests updated for short FQANs.

N.B. This will merge into dev but I will cherry-pick the commits onto the previous release once the changes are accepted. :cherries: