REST add a user search by external id, remove the login value of UserVO
if identity name are automatically generated

Adapt calendar web service to not use the identity name, add a new user
authentications web service based on identity key, remove the advanced
properties controller

Login happens only with authentication informations, identity name is
now only used for legacy directory name. User name of authentication can
be changed. LDAP users can be imported with LDAP::ldapUid. Users can be
imported in courses, groups... with First name last name.

A very minimal REST API to change the user visibility of course elements
results based on grading assignments.

Implement a CSRF token to protect a little more against CSRF attack.
Enhance the UI framework to allow opening a link in a new browser
window.

Use an opt-out flow for comments in video, springify notifications and
notifications handlers