Default connector implementation does not remove old connection instances

[tecc]

This causes it to use more memory if a program connects to multiple servers (and by extension, different ports).
There are a few requirements I do want to impose on a fix:

• Don't create a new thread per instance of the default connector. That's very inefficient.
• It should preferably be updated automatically.

I'm preoccupied with other issues at the moment (see #6) so I can't work on this one. Not yet, at least.