RBToolsConfig is now used throughout the codebase.

BaseCommand.config is now an instance of this, options now take this,

and base command support accesses state on this without the need for

conditional checks.
Options benefit the most. We can now get rid of all the custom

default= arguments on any option backed by a config key. The option

support has always based the default on the config, but only to reflect

values specified in config files. Since RBToolsConfig now manages all

defaults, the ones on options can be removed. That will happen in

another change, but the classes are prepared for it.

Unit tests pass.
I've been using this locally, and have used it to post this change and

other related changes today.