added lunar targets

[mikaelarguedas]

I assumed it's ok to have duplicate os_code_mapping values because they're always associated with the os_short_name so it shouldn't be ambiguous. Is that correct ?

[dirk-thomas]

On the status pages the tooltip of the column will show the long string so that should be ok. The only problem would be if a single ROS distro would span across both Saucy and Stretch since the Jenkins views would get merged. But that is not the case so I think this is good as is.