Add a new item.

Parameters:

• pID - the value of a radio button ( the radio's parameter 'value'). Required for 'radio' items only. For other controls - null
• itemData - the object of the item to add
• pos - the position to add the new item to

  // for radio button
myForm.addItem(value, itemData, pos);
  // for other items
myForm.addItem(null, itemData, pos);