Recipe collaboration

[pscn]

With #28 in mind, it should be possible to work on a recipe with other people. I'd imagine you could invite others to edit a recipe with you.

The recipe migration entries should then have a user reference so it's visible who did the change.

On entering a collaboration recipe we could provide real time updates e. g. through a web socket. Maybe also have a small chat area.

[daviddyess]

This would be even better if we could pull in everyone's flavor stash and use what each has available or all flavors available.

[pscn]

That could be done like ATF does at the moment:

• using a * to indicate it's in your stash
• using a + to indicate it's in another users stash
• using a ** to indicate it's in everybodies stash