Integrate eZ Publish authentication with Symfony SecurityComponent

Will probably need :

• Custom UserProvider
• New user/login (alternative is to rely on legacy)

Security doc : http://symfony.com/doc/current/cookbook/security/index.html

Specification document : https://docs.google.com/a/ez.no/document/d/1vEBwnY5Em6sjbkN8_YG6ANVh3B8eg8UwnFdq2heMsf0/edit#