Provide an API to map a port to a specific container in a composite container

Provide an API that allows mapping a port to a specific container.

One example use case is to map port 3306 at a specific IP address to mariadb that may be running in _one_ container in a composite container.

When an application with a unique port identifier matched to a composite container is found, a L2/L3 IP address is created with Neutron. All traffic for this address is then forwarded to the actual physical machine/port where the container that is part of the composite container is running. The source L3 IP address and target L3 IP address will definitely differ, and the port may or may not differ depending on scheduling limitations on the target container machine. If the composite container is restarted elsewhere, the target mapping should be dynamic and change accordingly.

The API should provide 3 operations
1. Create a port mapping
2. Delete a port mapping
3. Obtain information about a port mapping