Create and view performances

This feature turned out to be several:
*Create a performance
*View a performance
*View the date create and by whom
*Add multiple customers and multiple partners to a performance
*View all customers and partners associated with a performance
*View a list of all performances by customer

@ChristopherThorsen - please take a look
Instead of writing `where(organization_type: "Customer")` twice, I think you should write it once and then re-use that here.

Maybe I'm misunderstanding your objection?