(CFACT-59) Add id and gid facts

Hmm, we need doc comments on this.  I can't quite figure out why the doxygen build is silently allowing warnings on Travis:

    doxygen
    if [[ -s html/warnings.txt ]]; then
        cat html/warnings.txt
        echo "documentation failed."
        exit 1
    fi

Am I missing something?  That exits as expected whenever I introduce a documentation warning locally :/