Allow only vertical reorderingin sortable lists (#24062).

Patch by Vincent Robert.

git-svn-id: http://svn.redmine.org/redmine/trunk@15996 e93f8b46-1217-0410-a6f0-8f06a7374b81

public/javascripts/application.js

@@ -665,6 +665,7 @@ function beforeShowDatePicker(input, inst) {
     }, options );
 
     return this.sortable($.extend({
+      axis: 'y',
       handle: ".sort-handle",
       helper: function(event, ui){
         ui.children('td').each(function(){