(extensions) API for creating Artisan commands.

[prplwtf]

[prplwtf]

Implemented, requires testing.

[prplwtf]

We might re-do the implementation as it's not how I want to be done. We might go for a Components.yml approach requiring commands to be registered in a Artisan.yml while Blueprint does it's magic and calls the command's functions.

For applying these changes, we could just steal a couple lines of code from the components script, with the added bonus of having to do less with sed as these commands should be able to live in isolated files instead of thrown into a component.

[prplwtf]

I'd love to receive some developer feedback on this to see which implementation would benefit developers (and users) the most. I'll try to maybe get a working version before next release, but no promises.

[prplwtf]

Done! Just need Laravel schedules now and we'll have some awesome new extension APIs for next release.