get_user needs Among clause

[JnBrymn]

(Ref https://github.com/JnBrymn/minglbot/issues/25)

Add Among(...) and Not(Among(...)) clauses.

This is basically a filter on the results so that they will only include those "among" or they will exclude those "not among".

Considerations

• Need to have these members hydrated so that their names are actually in neo4j
• What does it mean when both "among" and "not among" are used?
• Where in the query to put this clause so that it is most effective at reducing query time?
  • As an independent filter before everything else?
  • Mixed in to the main WHERE clause?