In place of the deprecated service_proxy_auth setting of

/service-proxy-testauth/, provide sp_auth_credentials

Also this test page previously explicitly set pazpar2_url, which is no
longer necessary, so I removed that propertly.

*** These changes should be made to all example pages that use a
    special /service-proxy-XYZauth/ URL. All of those are gone, and
    should be replaced with their credentials only.