[r22172]Add translation to gen.merge.diff

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@22174 4ae1f11a-8b86-4847-b8af-ab372f36d1fd
[r22173]GrampsLocale: When checking translations check full locale first

So that e.g. en_GB will be preferred over en if en_GB is in fact the
desired translation.

git-svn-id: svn+ssh://svn.code.sf.net/p/gramps/code/branches/maintenance/gramps40@22175 4ae1f11a-8b86-4847-b8af-ab372f36d1fd