Some changes to the setup for test corpora in the backend:
All fixtures for creating an elasticsearch index are now function-scope (without repeated indexing), which means they can get access to a test database if needed (close #1533)
Moves all test corpus definitions to a centralised location (corpora_test)
Fixtures for providing the corpus name and the index are now in the project-level conftest
The CSVMockCorpus should now be equivalent to the JSON corpus definition.
Some changes to the setup for test corpora in the backend:
corpora_test)CSVMockCorpusshould now be equivalent to the JSON corpus definition.