Create a test battery to check use cases on arbitrary server

[Mec-iS]

Every use case in Specs should be turned into one or more TestCase in a battery of tests to check full compliance of an arbitrary server with Hydra specs.

UPDATE:
The battery is executed client-side, but the target endpoints are on the server; so the agent will run the tests on a target server to check if the server is compliant with Hydra specs. This is an additional set of tests to its own unit tests. This way python-hydra-agent can be both a client AND some sort of "Hydra compliance agent" that can test servers. There are lot of synergies in place between these two tasks, this functionality can improve both our knowledge of practical API development and the strength of hydrus if the tests are run against it.
By defining this test battery we achieve both objectives:

• we align the client to the use cases
• we test the server to be hydra compliant