add external authentification backends
- ldap (userbind)
- mail services (imap, pop3, smtp)

authentificated user (which not exists) will craetes autmaticlly
fix exception with uncatcht notice (insecure AUTH=PLAIN)
hide password fields when external auth-backend is used
now, the admin can en-/disable autocreation of users
Merge branch 'feature/auth-backends' of https://github.com/InuSasha/Baikal into sql-auth
Add framework method for getting instance of auth backend.
Add SQL authentication backend - set a query in config for checking credentials
The SQL backend might not allow user management (if in same table)
Options to allow SSL connections to MySQL server.
Restrict URI index to first 325 characters to avoid exceeding the 1000 limit (x3 see docs)
Merge branch 'mysql-ssl'