Set's the form field's value. For input boxes, this sets the value attribute. For
textareas, it sets the innerText. For radio boxes and select boxes, it removes
the checked/selected attribute from all, and adds it to the one matching the value.
For checkboxes, if the value is non-null and not empty, it checks the box.
If you set a value that doesn't exist, it throws an exception if makeNew is false.
Otherwise, it makes a new input with type=hidden to keep the value.
Set's the form field's value. For input boxes, this sets the value attribute. For textareas, it sets the innerText. For radio boxes and select boxes, it removes the checked/selected attribute from all, and adds it to the one matching the value. For checkboxes, if the value is non-null and not empty, it checks the box. If you set a value that doesn't exist, it throws an exception if makeNew is false. Otherwise, it makes a new input with type=hidden to keep the value.