Confusing environment configuration

[stevenbenjamin]

There are a number of confusing env variables that should be simplified.

• variable names in toml files don't match names in env variables. This makes it potentially confusing to add a PORT variable to fidesops since there's already one in the toml, though it is then mapped to FIDESOPS_REDIS_PORT.
• we have env variables in 2 places in the docs, /deployment and /how-to guides/configuration reference.
• our "TESTING" env variable actually just controls switching the name of the database, so it doesn't really correspond to anything like "in testing mode" (e.g. if you try to use it to enable reloading, or logging, trying to use those modes ends up pointing the app to a database named "test"). We should probably just use the database name.