WebProxy Gateway SSO type

[Chris Beach]

Hello folks!

I am working to upgrade Spring in the WebProxy portlet.

I'm interested who is using the `GatewayPortlet` type - https://github.com/uPortal-Project/WebproxyPortlet/blob/master/docs/gateway_config.md.

I'm not aware of any adopters using the Gateway SSO type. Assuming that holds true, any concerns with removing this type from WebProxy?

Thanks,

Chris