cas 6.x-2.0

This release adds the following features:
* CAS Single Sign out support
* Checking to make sure a user is logged in first
* Logging via the regular Drupal user login block.
* Ability to exclude specific page patterns from the login and first login checks.
* A minimal cas server version for connecting drupal sites together via cas. (note requires SSL Support).

Also provides fixes for :
#180608: Blocked users can still login
#482080: cas_logout formats the destination url incorrectly
#258909: Please do not randomize my password on every login
#282917: Problem with Hide email and password options