(For now) don't show error popup

Suppress the error popup window for uncaught JavaScript errors. It's
showing up for all uncaught exceptions, even ones that aren't critical
failures. We should hide this until we have a better way to make it less
obtrusive or only show it for truly critical errors.

Work-around for #634
Include page location in JavaScript error log.
Update changelog
Merge branch 'hotfix-634-turn_off_error_popup' into develop

Conflicts:
	README.rst