Adding policies for KeyStore MAC.

Add keystore_key class and an action for each action supported
by keystore. Add policies that replicate the access control that
already exists in keystore. Add auditallow rules for actions
not known to be used frequently. Add macro for those domains
wishing to access keystore.

Change-Id: Iddd8672b9e9b72b45ee208e6eda608cc9dc61edc