Authentication and Identity framework

[jlfranklin]

Linking Drupal 7 sites to other user databases, such as LDAP or web services, was always clunky at best. There were a number of reasons for this, including:

• Only one set of password checking functions could be active.
• Assigning them meant creating a line in settings.php
• Non-password based systems (e.g., SSL certs) had to figure their own way to link in.

Silkscreen needs a well thought-out system that can handle a number of identity and authentication needs, including:

• External user databases (e.g., LDAP, another Silkscreen instance)
• Two-factor authentication
• Client SSL certificates
• OAuth