RR add a mode to connect to a RR replay port

Seer supports (but is currently broken #307) a way to run "RR replay" directly.

This task adds a mode to Seer to connect to a "RR replay" port.
```
$ rr record -n --output-trace-dir=/path/to/rr/trace-directory  hellorr arg1 arg2

$ rr replay -s 50505 -k /path/to/rr/trace-directory

$ seergdb --rr --port localhost:50505 --sym hellorr
```
