Query parser unit tests

This MR includes

• Extensions to existing unit tests for the event query parser
• An entirely new set of tests for the search view
  • unlike the existing query parser tests, these can also handle labels in the queries
  • the downside is that they require a test DB be set up, whereas the existing tests were more general in that they tested the Django Q object used to query an arbitrary DB
    • future parser improvements should make it possible to accomplish everything with Q objects, making these tests less important