Add tunnel quantity configuration.

At the moment, there is only length  and variance configuration present under I2P settings.

Tunnel quantity configuration is also important as it helps in managing swarm speed & optimize as well as serve backup for clogged or extremely slow tunnels.

For example, if there are 100 cars and only 1 tunnel lane the traffic will be congested and slow. But if there are 100 cars and 8 lanes in the tunnel the traffic can be divided properly and will not congest as previously.

Hence, it is important to provide this settings.

And, no, sometimes default configuration does not work properly as all participants do not have same I2P speeds.