Use hostmasks for PRIVMSGs, reply to server PINGs, fixes

1. Send new lines as new messages. 
Multiline messages currently get corrupted. The first line is sent correctly, but the second is sent as is (without being formatted for IRC) and is not understood by the client.

2. Hostmasks for PRIVMSGs. 
This seems to be the standard and allows ignoring people or similar without conflicts, especially if the first name is used instead of the full name (requires a manual edit).

3. Reply to PING requests. 
This is so clients don't disconnect every now and then, when pickups doesn't reply to PING messages.

4. Segmentize messages correctly. 
Links aren't clickable without this.
I think `if line:` would be more pythonic.