[FIX] E-mail user indexing - add to conference

 * If user was registered in a conference before having an account (same e-mail), his/her identity will be automatically tied to the registration in question;
[FIX] SSO allow public external accounts

- e.g. Google or Facebook
[FIX] Backporting fix from master to v1.1
[ADD] New lecture/meeting style for TICAL project
Merge branch 'v1.1'

Conflicts:
	indico/MaKaC/authentication/NiceAuthentication.py