Couple of minor changes to the template that's used to generate the
submission script:
1) Use the offical 3.0 release of Mantid (instead of 2.4)
2) Add the Mantid plugins directory to the LD_LIBRARY_PATH
Cleanups to SnsLdapBackend:
1) Explicitly set the supports_inactive_user attribute. (Django issues a warning if it's not there)
2) Add exception handler for ldap.INVALID_CREDENTIALS so we don't print debug messages when someone gets their password wrong
3) Change how we print out the other ldap exceptions.  (Python says BasicExcpetion.message is now deprecated)
4) When creating a new user, call set_unusable_password() instead of leaving the password field empty.