Merge pull request #625 from JensErat/locking

[FIX] Core, Locking: fix semi-global lock when no database is opened
[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]
[MOD] XQuery, XSLT Module: redirect error feedback to XQuery processor
[MOD] XQuery, output of detailed query info unified for API and command
[MIN] GUI, Editor, Shift-TAB: unindent current line
[MIN] GUI, File Dialogs: textual filters for XML, JSON, ... added
[ADD] XQuery, Profile Module: prof:human(...) added; formats numbers in
      a human-readable representation
[ADD] GUI, Info View: hyperlinked error messages. Closes #628
[MOD] GUI, Ctrl+.: jump to next error, even if placed in another file!
[MIN] GUI, Save dialog: add file suffix only for activated file filter
[FIX] GUI, Editor: history set back to original value.
[ADD] GUI, Search Panel: red highlighting if no hits are found
[FIX] XQuery Update: fn:put() does not work with file: URIs
[FIX] XQuery, Java modules: unload after parsing queries