Remove render blocking resources from web proxy

[amoeba]

The HTML template the web proxy uses puts two render-blocking resources in the head tag. I noticed this because loading the page is noticeably slow. We should move these down into the end of the body so they don't render-block.

https://github.com/DataONEorg/slinky/blob/102941f33b053aa40f14d21e9c1e4481ba8e6e6e/deploy/docker/web/templates/base.html#L6-L9

While we're at it, there are a few more things we should change. Here's the full list:

• [ ] Move render-blocking resources out of the head tag
• [ ] Serve all resources our own origin rather than unpkg
• [ ] Don't hard-code the location of any resources, instead load resources from the appropriate location regardless of deployment context

I might make some style/layout tweaks while I'm in here too.