Filter the mdattr namespace out of all output pipelines.

This allows us to add entity attributes to fragment files without them being published anywhere.
Add mdattr and saml namespaces to newly imported fragment files.
Update normalised fragment file template to include mdattr and saml namespaces.
Typo: check against the correct namespace for RegistrationInfo.
Add very basic but generic ruleset for mdattr (entity attributes) specification.
Add UKf-specific rules for entity attributes.