Can't point several puppet modules directories for plugins

When you do puppet apply, this command allow to set several directories for modulepath, separated by semicolon. It would be really nice to allow such syntax for plugin tasks in 'puppet_modules' value. It will allow us:

1. Use internal functions from osnailyfacter (like get_nodes_hash_by_roles)
2. Create much smaller plugin size by not including duplicated puppet modules to dependencies (it's normal case when plugin needed stdlib, concat, apt and so on which we already have as fuel-library dependencies)