Attributes: add missing optional attributes

Add attributes defined in AAF and Tuakiri vocabulary as
Optional/Recommended but so far missing in attribute validator:

* auEduPersonLegalName
* auEduPersonAffiliation
* eduPersonPrincipalName
* eduPersonPrimaryAffiliation

Add corresponding validation methods (but permit blank as these are
Optional attributes).

Add mappings in application_config - using the usual SP name of the
attributes.

Add corresponding validation error messages.

Add tests.

All tests passed.

Implements #7 (now that I see it exists as a recently created issue).
Attributes: update default mappings

Update default mappings for the authenticationMethod and
organizationalUnit attributes to use their usual SP name.
Merge develop-add-attributes (#16) into code-develop
Merge code-develop (#16) into tuakiri-develop

Resolved Conflicts:
	grails-app/i18n/messages-domain.properties
Branding: apply branding to new merged code (#16)
Branding: apply Tuakiri branding to PDF export CSS

Apply Tuakiri branding (styles & colours) also to the built-in CSS
styles in _snapshot_pdf.gsp for PDF export.