Move the test user preparation function out of the backend manager.
Add helper function to prepare an object type on a backend to be used by tests.
Make the c++ file test use its own backend
Make the QML tests use their own backend.
The tests do not require the ENGINIO_BACKEND_ID and ENGINIO_BACKEND_SECRET
environment variables any more since they manage their own separate backends.
Merge pull request #139 from bbandix/perTestBackend

Move remainig tests to their own backend