(maint) move validation failures to #validate def
(maint) move validation failures to #validate def

Previously, the validation procedures were occuring in the #munge
method. This was a problem because if #munge raises an exception, the
error displayed to the user is opaque. If the data input is not valid,
the error should be raised in the #validate method. This will ensure
that the output given to the user includes information about the class,
resource, and parameter which is in error.

puppetlabs/puppetlabs-registry