Added peer addresses to description string.
Added ability to update a TMFPeer instance with a NSNetService instance.
Set log level to error.
Changed peer UUID persistance.

Each peer within 3MF has an unique UUID for identification. This identifier has been changed on every full app restart before. IT seems, that Bonjour reuses net services instances even if an app restarts and this behavior caused identification issues leading the connection refused error in issue #1. Big thanks to @caylanlarson for debugging and pointing in this direction!
Discovery peer visibility improvements

- peers are marked as visible after an additional heart beat message (hand shaking)
- peers will not get reported as available before the local peer's service is resolved.
Merge branch 'refs/heads/Fixes/connectionrefused' into develop