Google will create an entityId with your domain, as described in #9.

Might not be complete, needs check with current G Suite interfaces.
But improves on the current situation.

It can now be used with \SimpleSAML\Auth\Simple, although the old name still works too.

Also tweak wording of artifact idp docs a bit re memcache extension.

I may be missing something but I haven't found a way to add the --ssl-ca
MySQL option to my database connection. It appears we just need to pass
in an $options param.