This eases up suggested initatives from http://mantis.tokeek.de/view.php?id=649
Allows longer term also to store translation maps for the htroot files
in standardized/reuseable xliff format ( http://docs.oasis-open.org/xliff/xliff-core/xliff-core.html ).
+ added test case creating and comparing xliff file with internal custom prop file.
(currently the introduced class is not used in core code)
reger