[plugins:puppetdb] Fix debian package name

As it can be seen in

http://deb.theforeman.org/dists/plugins/nightly/binary-amd64/Packages

the package is ruby-puppetdb-foreman, hyphenated as all other foreman
plugin debian packages.

Fixes GH-256
[plugins:docker] Initial Docker plugin support

Fixes GH-257
[plugins:digitalocean] Initial Digitalocean support

Fixes GH-258