Unify security service configuration

Currently, there are four security configuration files in /etc/security:

The default security configuration (mh_default_org.xml) and three example security configuration for CAS, Shibboleth and LDAP.

The CAS example seems heavily out-dated, the Shibboleth example is obsolete since part of the default security configuration and the LDAP example is up-to-date.

To avoid having to keep four different security configuration files in sync, we decided to unify those four files by creating a default security configuration that contains everything needed to get CAS, Shibboleth and LDAP running - although CAS, Shibboleth and LDAP will be disabled (in means of commenting the configuration) by default.