(MCO-314) mco plugin package should support 'lib layout

This commit enables the plugin packager to support plugins using the
'lib layout'. Since this layout also suggests using sub directories in
the main plugin directories (for example
mcollective-shell-agent/agent/shell/*) this commit also extends the
plugin content lookup to include subdirectories.

As result, this means that the plugin packager will now either package
everything in $plugin_name/lib/mcollective/ or $plugin_name/, depending
on the chosen layout.
(maint) - Fix modulepackage packager when passed a path on the cli
Merge pull request #264 from ploubser/mco-314

(MCO-314) mco plugin package should support 'lib layout
(MCO-466) Add search of $libdir/mcollective/agent/$agent/$action to implemented by

The commit d9d4354 implemented a default search path for scripts
supplied as parameters to #implemented_by. However the path did not
correspond with the path described in the feature ticket
http://projects.puppetlabs.com/issues/13064

This commit adds the previously described search path with the aim of
deprecating the incorrect search path in the future.
Merge pull request #265 from ploubser/mco-466

(MCO-466) Add search of $libdir/mcollective/agent/$agent/$action to impl...