Fixed the subscriber model a bit
Added the concept of 'set'-able variables to the Ui, and added auto-attach and auto-command to it
Handle overflows in seq/ack properly
Greatly improve the UI model
Some cleanup to the 'ack' code
Fix an issue that was causing retransmissions to snowball when one happened (every message used to trigger a new transmission, even if it was a duplicate ack; now, only messages that acknowledge new data trigger a retransmission)