Add REST API endpoint to get ports (needed for port forwarding).

Output example:

    curl  "http://node1.domain.com/token/__test__/container/ports?r=0001"
    [{"Internal":8080,"External":4343}]

Only exposed ports are available for forwarding. Syntax is

    ssh -L <local port>:127.0.0.1:<External port> user@hostname

Example:

    ssh -L 9000:127.0.0.1:4343 gear-0001@node1.domain.com

This would connect 9000 on the local machine to port 8080 on the gear.
Merge pull request #63 from kraman/get_ports

Add REST API endpoint to get ports (needed for port forwarding).