12597 - add a modulepackage packaging target

This patch adds a modulepackage target to the mco package builder.

Usage:

   $ git clone https://github.com/ploubser/mcollective-puppetdb-discovery
   $ cd mcollective-puppetdb-discovery
   $ mco plugin package \
        --format modulepackage \
        --vendor puppetlabs

This will create a module for the forge named 
puppetlabs-mcollective_puppetdb_discovery containing the source code and the
class mcollective_puppetdb_discovery::discovery

This is somewhat cargo-culted from the RPM packager