Renamed files to support gettextizing with intltool.

Renamed files to support gettextizing with intltool.
    page-sizes.paper -> paper-sizes.xml
    predefined-labels.template ->predefined-templates.xml

xml-paper now looks for files with ".paper" extension or exactly named
"paper-sizes.xml".

xml-template now looks for files with ".template" extension or ending with
"-templates.xml".

Gettext is run on attributes starting with "_" in both xml-paper and xml-template.

git-svn-id: https://glabels.svn.sourceforge.net/svnroot/glabels/trunk@263 f5e0f49d-192f-0410-a22d-a8d8700d0965