chore(client/js/handler.xhr.js): Log XHR upload response status and text

This should be enormously helpful when assisting a user with an incorrectly configured server or a server-side script that is not returning a valid response.
docs(docs/integrating/options/s3.jmd): #899 - successRedirectEndpoint request property, adjust TODO
docs(S3-related): #899 - TODO notes for required 3.8 adjustments
fix(docs/integrating/quickstart/index.jmd): Don't hardcode FU version in link tag
docs(docs/server/s3.jmd): #899 - server-side documentation