[IDEA] Allow managing a list of connection servers

[strk]

I would find it useful to have a named list of connection servers to use depending on what I'm doing. For example, for finding people to jam with, it would be useful to have a connection server that is known and used by people nearby myself.

I could create such a connection server and share it with others but it would be hard for them to switch between that one and some other one unless there's a way to select from a list of connection servers.

At the moment when I use my own connection server I always also have trouble remembering what the default connection server string was, for instance. A manageable list would instead always have that one.

Each item in the list might also get a name, for ease of operations. Like anyone could start multiple connection servers on multiple ports and dedicate them to different musical generes, like Jamulus does with "directory servers". At that point it's easier to pick "jazz" or "rock" rather than a combination of an IP and a Port.