Test clean up (moved things in to `setUp`, removed unnecessary `tearDown`).
FilterType.expectsPossibleValues is now consistent with what's used on the front-end.
`Filters` are now only considered valid, when initialised with `possibleValues`, if they are of the appropriate type.
Fix for #893 - ignoring possible values given by the WFS scanner where necessary.
Fix for #893 - a bit of jquery to only allow user to enter possible values for String filter types (corresponding to what is allowed on the back-end).
Fix for #893 - clean up possible values which aren't used.
Updated test for #893 fixes.
Merge pull request #906 from aodn/issue_893

Issue 893