[FIX] XQuery, GH-605: relaxing condition on empty string comparisons
[MIN] slower refresh of dialog progress bar
[MIN] Util.debug() calls revised and simplified.
[MIN] Show stack trace in all error outputs
[FIX] XQuery, base64 streams: compare contents instead of input path
[MIN] Checkstyle updated to latest version of eclipse-cs
[MIN core preference file updated]