Episode contributors: Add ability to query and add individual hosts for a specific note

Parent: [EPIC] UI extensions based on the new fields pr... (#146 - closed)

A show has a fixed, general set of hosts. These hosts are assigned via the show page.

As per the recent data-model changes, now also Episodes (=Note), can have individual Hosts assigned.

Now the Edit Note dialog should work like this:

• Pre-populate the contributors field with the hosts set in show.hosts
• Users can add additional hosts (which are not part of the general show) or remove any hosts which are usually assigned to the show