Branding: move AAF mentions from GSP to messages

Extract AAF specific mentions out of GSP code under
app/federationregistry/grails-app/views (403.gsp, 404.gsp and 500.gsp)
and move the text into messages-branding.properties.

Notice: some of the text includes HTML formatting and is rendered
WITHOUT the HTML encoder.
Branding: Fix typo in messages-branding.properties
Branding: add missing cosmetic newline

Add missing cosmetic \n in messages-branding.properties
Branding: Email templates: move text into messages

Move explicit references to AAF and AAF support from GSP email templates
(email.gsp and workflow email templates) into
messages-branding.properties
Branding: extract branding from login error pages

Extract AAF specific text (federation name, support link) from login
error pages (federatederror.gsp, federatedincomplete.gsp) into
messages-branding.properties
Branding: removed AAF references from non-branded messages.properties

In app/federationregistry/grails-app/i18n/messages.properties, there
have been three entries refering to AAF:

* views.fr.index.overview.descriptive: this one was unused - and now part of branding.fr.welcome.header

* templates.fr.certificates.validation.invalidca - there were two entries
  with the same key, the second one (with no direct AAF reference was used),
  so deleting the first entry with AAF reference.

* help.fr.organization.displayName - drop "AAF" from the discovery service reference
  - change "AAF discovery service" to "discovery service"
Merge pull request #127 from University-of-Auckland/aaf-develop

Branding: move AAF mentions from GSP to messages