cfme_data now autorandomizes certain values

- See utils.randomness.RandomizeValues docstring for more info
- See utils.cfme_data.CfmeData docstring for usage
- Moves loading of cfme_data file into a util function, example usage in updated test_vm_power_control test generator
- Renames cfme_data fixture file name to match the fixture name
- Moves random_* fixtures into their own pytest plugin
- Removes superfluous random_string fixture definitions buried in the tests tree
- Given the mildly crazy things happening in RandomizeValues, there are unit tests for it in utils/tests
- Moves some other things around in utils
- fixes #65