Keep attribute order in XML file for debug version

Keep the DOM attributes in the same order each time a file is saved.
Therefore, don't use QHash for security relevant things from here on.
See
http://qt-project.org/doc/qt-5.0/qtcore/qhash.html#algorithmic-complexity-attacks
for details.

This is only active if build with DebugFull or DebugKMM and not used in
production code.