Support multiple port mappings for same internal port

Signed-off-by: Andrew Burkett <burkett.andrew@gmail.com>
Move to build_port_bindings(). Added Tests

Signed-off-by: Andrew Burkett <burkett.andrew@gmail.com>
Merge pull request #624 from drewkett/multiple_port_mappings

Support multiple port bindings for same internal port
Bash completion for fig command