Supports multiple tunnels at the same time

Sometimes I need to set up multiple tunnels, and I have to run multiple brook processes at the same time.

What I want is something like this:

brook relayoverbrook \
    --link "brook://wssserver?password=PASS&wssserver=wss%3A%2F%2Fexample.com%3A443%2F" \
    --from 127.0.0.1:3306 --to remote-db.example.com:3306 \
    --from 127.0.0.1:6379 --to remote-redis.example.com:6379 \
    --from 127.0.0.1:8080 --to remote-web.example.com:8080

or like this:

brook relayoverbrook \
    --link "brook://wssserver?password=PASS&wssserver=wss%3A%2F%2Fexample.com%3A443%2F" \
    --tunnel 127.0.0.1:3306,remote-db.example.com:3306 \
    --tunnel 127.0.0.1:6379,remote-redis.example.com:6379 \
    --tunnel 127.0.0.1:8080,remote-web.example.com:8080

Allowing multiple --from --to parameters to support multiple tunnels in a single process instance.

Start at the relayoverbrook command and inspect how its --from and --to parameters are parsed and used. Compare the current single-tunnel behavior with the requested repeated parameters or --tunnel form. Done means one brook process can establish all three example tunnels concurrently without requiring separate processes.