For release creation switch to a better system for adding artists

[rtman]

Currently we present a list of all artists, this will quickly become unwieldy.

Accounts should some how be connected then that provides the list of available artists to choose from. Will need to decide how to add new artists, probably a switch, the user will have to know if the the other account is created or not in some way.

[rtman]

Each creator account has a unique code that another creator can use to connect with them and then this then allows labels to create releases/supporting artists with that artist or artists to create supporting artists with that artist.

Each user account can invite via email another person.

[rtman]

#91

[rtman]

#115