Consider extension refactor

[Brickster]

$ git state extensions
# lists extensions

$ git state extensions log [--run]
# runs to extension and is the default

$ git state extensions log --command <command>
# edits the extension

$ git state extensions log --command <command> --run
# edits the extension then runs

$ git state extensions log --config
# prints the config

$ git state extensions log --command <command> --config
# edits the extension then prints the config

$ git state extensions log --delete
# deletes extension

This way they all play well together and the only mutually exclusive options are --run and --config and anything with --delete.

[Brickster]

Initial implementation added in v0.7.0 but ultimately needs some fine-tuning.