hacketyhack! add support to install plugins from package

this is a butt-ugly hack to allow installation of mco plugins
with packages from puppetlabs repos.

hack #1:

this wraps the old code into mcollective::plugin::puppet to
install plugins from a puppet fileserver, using the default
value for the param source ('puppet') for mcollective::plugin.

using source => package will pass the name on to
mcollective::plugin::package which will resolve the package
names (only tested on ubuntu ...).

hack #2:

using a plugin name prefixed with "mcollective-" will pass the
name straight to the package resource allowing to work around
the pkg name magic of hack #1.

I know ... WTF.
add manage_modules param to mcollective::server

gives us a choice wether we want the puppet fileserver-sourced
or packaged modules.