Enable tests to be run independently

[ialarmedalien]

Each set of tests (/spec/test; /relation_engine_server/test; /importers/test; /client_src/test) should be runnable on its own, including performing the appropriate set up (schema loading, etc.) for the db. Ensure that the test classes/test suites do the correct set up and that tests can be run in any order.

[jayrbolton]

A feature I would like to have is the ability to run unit tests separately from integration tests, where the unit tests run very fast (so we can get a faster development feedback loop). Unit tests should import and test python code directly without running any docker containers or servers.