This renames the existing option_list usage on BaseMultiCommand to

common_subcommand_option_list, and re-enables option_list as the

options for the main commands on the multi-command.
Through this, it's possible to have commands that take their own options

separate from those on subcommands.
We also inject global options, ensuring that rbt <maincommand> --help

will show --help, --debug, and --json as options.

Verified that rbt review still functioned correctly. rbt review --help

now shows standard options, and subcommands are all sharing the common ones.