Added optional "remote ports forwardings" settings in advanced slave settings

Hi,
I've added an optional "Remote Ports Forwadings" field in the advanced SSH field, that allows remote ports on the slave to be forwarded to the master.
I need this so that my SSH slaves do not need to know the IP address of Sonar and Sonar database.

If a comma-separated list of ports to forward is entered in the field then these ports are forwarded.
This is equivalent of -R localhost:port:localhost:port SSH options.

I hope you'll consider adding my changes to the official plugin code base.