[Authenticated Feature] List of Available Servers

[JoelProminic]

@JustinProminic and I did some more brainstorming on returning a list of available servers for #676. This interface would return of servers available to the user from their Prominic customer account. This should include both Domino and non-Domino servers.

The Domino server list can be used to make it easier to select a target server for the Domino projects (#668, #669, #646, #670). We should still allow the user to enter the server name manually, though.

I will need to write an agent that can lookup and return the servers for the user. I have similar agents already, but I think we will want a version that returns the servers from all customer accounts that the user has access to, rather than a single account.