multiEdit: Support default value and description

-If 'defaultValue' is specified for a text field, then put that value
 into the text field on load.

-If 'desc' is specified for any field, then use it as a 'title'
 attribute to show a tooltip description.

Example:

      'icmptype': {
        ...
        defaultValue: '-1',
        desc: 'Please specify -1 if you want to allow all'
        ...
      }

ui/scripts/ui/widgets/multiEdit.js

@@ -782,6 +782,7 @@
                   );
 
             if (field.isDisabled) $input.hide();
+            if (field.defaultValue) $input.val(field.defaultValue);
           });
         } else {
           var $input = $('<input>')
@@ -794,6 +795,7 @@
                 .appendTo($td);
 
           if (field.isDisabled) $input.hide();
+          if (field.defaultValue) $input.val(field.defaultValue);
         }
       } else if (field.custom) {
         $('<div>').addClass('button add-vm custom-action')
@@ -821,6 +823,8 @@
           _l(args.add.label)
         ).appendTo($td);
       }
+
+      if (field.desc) $input.attr('title', field.desc);
     });
 
     // Setup header fields