refactored tests into 24 separate tests

[HJLebbink]

Note: depends on #114

Refactored one large test into separate tests. It runs 2 twice as fast as a result

[donatello]

Please fix conflicts @HJLebbink

[HJLebbink]

Please fix conflicts @HJLebbink

@donatello I rebased. Two minor issues with the code.

1. Every test is responsible for removing the stuff it created. But if the test fails the remove_bucket_helper may not be called.
2. TestContext.new_from_env (that reads the environment variables) only works with the configuration used by the build server. For a setup with play.min.io or my local box, it has bugs reading the env variables. A fixed version TestContex.new_from_env_new fixes that, but it does not work on with the build server.

[HJLebbink]

@donatello

I fixed that tests may not always cleanup their stuff.

PTAL