Showing owner as well as editor of a public collection

[envycontent]

Collections operate in a slightly different way to series and talks, in that they are 'owned' by one user who can share them with others.

The collection view lists the people the collection is shared with, but not the owner. It would be helpful to have the owner in that list as (i think) the owner is the only person who has full rights over the collection and can add other people.

(As admin, I can't edit collections, so if I'm asked to add someone to a collection, I can only do that if I take ownership using the change ownership interface - which is a bit of a fiddle, but could be avoided if the owner were listed)

[envycontent]

See #493