Support for permanent links maintained by both ends

[iAmGroute]

By separating the 'client' and 'permanent' conditions, it's possible to have links that are configured and maintained (re-established after disconnect) on both ends.

[iAmGroute]

After da516b2, it is possible for both ends to be configured as clients (and have listeners that trigger Link.connect). Further testing is needed to see if a deadlock is reached if both ends try to connect at the same time.