Add remove function

Author: haslinghuis

src/js/ConfigStorage.js

@@ -37,5 +37,11 @@ const ConfigStorage = {
             tmpObj[element] = input[element];
             window.localStorage.setItem(element, JSON.stringify(tmpObj));
         });
+    },
+    remove: function(item, callback) {
+        window.localStorage.removeItem(item);
+        if (callback) {
+            callback();
+        }
     }
 };