Re-add support for the Hiera ENC

Hiera support was previously stripped from this module for reasons
unknown to me; given that we have params class by now that all other
functions use to get their functionality parameters, we can simply
integrate Hiera back into that params class. The new workflow is like
the following:

1. Check if there is a configuration parameter stored in Hiera
2. Check if there is a configuration parameter specified in the
   environment
3. Use default or exit with an error message if the parameter is
   required