Document more dependencies.

List of dependencies was generated with this ugly script:
    find . -name \*.so | xargs ldd | grep " => " | sed -e "s/^.* => //" | \
        cut -d' ' -f1 | sort -u | xargs -L 1 pacman -Qo | \
        sed -e "s/.* is owned by //" | cut -d' ' -f 1 | sort -u
Gitlab: Move .secret into /etc/webapps/gitlab/secret

Have a post-install step create that file and ask the user to verify
it really contains a random string.
Gitlab: Fix PKGBUILD to actually run
Gitlab: Use tmpfiles.d to create directories in /var as needed