DEICH-6408 - Fixed JS hangup on error from server while saving
Also added more user-friendly alert message to the user. General handling of HTTP status errors (401/403/500 so far). Removed deepClone, and added a more capable seepCopy to lib/util.js. Removed fetch polyfill try-catch in util.js. Polyfill is not used any longer.
Closes DEICH-6408