fix(api): reset existing formdata for proper renewing

The apis formData collections always extended an already existing data value. If this however already contained properties of the same names as the formfields those were extended as well.
This led into situations where you want to reuse the same api several times. Especially for multiple name form fields like dropdown those always kept the previous values when submitted multiple times

Author: lubber-de

src/definitions/behaviors/api.js

@@ -443,6 +443,9 @@ $.api = $.fn.api = function(parameters) {
               } else {
                 formData[element.name] = element.value;
               }
+              if(hasOtherData && data[element.name]) {
+                delete data[element.name];
+              }
             });
 
             if(hasOtherData) {