Fix varnish chunked and general improvements

Make varnish play nice with chunked responses from media proxy. This caches chunks for 10 minutes which is more than enough time to have partials stored in memory. The full file will get cached and replace the chunks, so the TTL of 10 minutes here is no problem.

Also some cleanup for consistent indentation and removal of piping all requests to the backend by default. Piping everything is really not great for performance. Objects that can't be cached won't be, and that's most of the backend responses due to cookies.

Streaming is also enabled by default in varnish, so explicitly enabling it here is wasteful. Etags don't have to be stripped. Support more file extensions for caching media/static objects.