Auto update listings to include a newly added moderator

[drwasho]

When the user selects another moderator to add in the settings, any of their existing listings don't have that new moderator included in the contract. What the user has to do is edit the contract in order for the new moderators to be added. The more contracts they have, the worse this UX problem is.

Ideally when new moderators are selected in Settings, all of the listings should auto updated to include them. This is really important as we've found that users are quick to add listings before they add moderators, which weakens the transaction security... what's worse is that the user doesn't intuitively know that they need to update their contracts to add moderators, and they shouldn't have to anyway.

[drwasho]

Also applies to newly removed/blocked Moderators. If the Vendor finds that one of the Moderators is not responding or performing badly, and removes them, all of their listings need to be immediately updated... otherwise the Moderator will still be involved in transactions.