added cas-auth plugin. Basically a clone of the pin3-auth plugin, but with the following changes:
the CAS logout url is now defined in the wp-config-<local><stage><dev> file as is the name of the HTTP header being returned from the server.
Excised text references to pin3 to the extend practicable.
added CAS config attributes to wp-config
Merge branch 'develop' into staging

* develop:
  added CAS config attributes to wp-config
  added cas-auth plugin. Basically a clone of the pin3-auth plugin, but with the following changes: the CAS logout url is now defined in the wp-config-<local><stage><dev> file as is the name of the HTTP header being returned from the server. Excised text references to pin3 to the extend practicable.
added new header value to pin-proxy plugin