Move users and usergroupmembers tests to the per-testcase backend.
Move away from legacy object naming for fulltext search test.
Extract initial user and usergroup creation into a helper function
and move it to the backend manager.
Also move the fulltext search helper function definitions out of line
in the client test.
Move 'todos' object operation CRUD tests to per-testcase backend.
Move identity and acl tests to per-testcase backend
Move EnginioModel test to per-testcase backend
Merge pull request #136 from bbandix/perTestBackend

Make EnginioClient and EnginioModel tests use their own backend