merge -r21965 from trunk fix web service optional array parameters were always transformed to arrays

git-svn-id: http://piwigo.org/svn/branches/2.5@21966 68402e56-0260-453c-a942-63ccdbb3a9ee
merge r21983 from trunk
use right flag for sl_SI

git-svn-id: http://piwigo.org/svn/branches/2.5@21984 68402e56-0260-453c-a942-63ccdbb3a9ee