Improve test coverage for oae-search

api.js:

- Register a search type that already exists
- Register a document producer that already exists
- Rename all instances of documentProducers to searchDocumentProducers
- Test non-allowed refreshing of the index

internal/elasticsearch.js:

- createIndex, deleteIndex, etc. need validators

searches/general.js:

- Search as an admin to make sure everything comes back

util.js:

- Execute getSearchParams without query
- Execute filterNot
- Execute filterAnd, filterOr, filterTerms, filterTem and filterMemberships with invalid options