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)
Main image processing is now in ImageViewer, used by both ViewImage and
ViewFavicon.
Fixed URIMetadataNode.getFavicon to use non-standard icons with no size
ass fallback.