Right now a lot of different places modify resmoke's global configuration and the configs for spawned processes. These are stored in raw python dicts. We should create a dict-like configuration class that manages these configs, storing every access or update, and lets us view the history. We should also be able to assert the consistency of the configuration. This will reduce the risk in large changes to fixtures.
(As a bonus, this will make it easier for people updating fixtures, suite definitions, etc to understand how the mongo/d finally gets run.)