Update Login Module.

- Added an API to mange user OAuth authentication.
   - Updated the Filter to use the new API.
   - Updated the Module to initialize if it needed the storages needed by the login module.
   - Updated gmail callback to use the new API.
   - Added a Persistence Layer

CMS_USER_API
   - clean api and related persistence code.

src/persistence/user/cms_user_storage_null.e

@@ -108,23 +108,4 @@ feature -- Change: User password recovery
 		do
 		end
 
-feature -- Change User Oauth
-
-	new_user_oauth2_gmail (a_token: READABLE_STRING_32; a_user_profile: READABLE_STRING_32; a_user: CMS_USER)
-			-- Add a new user with oauth2 gmail authentication.
-		do
-		end
-
-	update_user_oauth2_gmail (a_token: READABLE_STRING_32; a_user_profile: READABLE_STRING_32; a_user: CMS_USER)
-			-- Update user `a_user' with oauth2 gmail authentication.
-		do
-		end
-
-	user_oauth2_gmail_by_id (a_uid: like {CMS_USER}.id): detachable CMS_USER
-		do
-		end
-
-	user_by_oauth2_gmail_token (a_token: READABLE_STRING_32): detachable CMS_USER
-		do
-		end
 end