Portal messages customisation

Enhance the portal messages customization options in mails, pages, corpora, etc.

Solution

• Remove all BFM references (mails, webpages, UI)
• Add more string replacement using the portal configuration Strings (PORTAL_NAME, ADMIN MAIL, WEBSITE URL, etc.)

(from redmine: issue id 2893, created on 2020/09/15 by Matthieu Decorde)

added administration type::task + 1 deleted label

changed milestone to %Portal 0.7