Users can be filtered with LIKE clauses

In order to allow easy assigning of users, I've taught the API to
accept 'fuzzy' matching on two possible text fields on the user
record. API parameters are passed to the DB API, which parses through
kwargs and determines whether the parameter is on the model queried,
and whether it should be filtered using LIKE or ===.

Change-Id: Ia676506e5944e2be06c615b04be4d7cee33839a7