Running multiple terras at once

[andyneff]

Since Terra logging uses tcp port 9020 by default,. it becomes tedious to attempt to run multiple terra apps on the same computer (even as different users). Currently you have to set the terra logging server port manually in your json config file.

I think a good default behavior here would be to try and check that the default port is open, and then auto increment it by one until a free port is found.