Returns a String that can be used as parameter name for input elements.
Subsequent calls will return different values to ensure uniqueness of
parameter names within a form.
Like
Form.createUniqueParameterName() this method returns a String
that can be used as parameter name. Since most modern browsers keep track
of previously entered values (with the same parameter name) a desired
name can be passed to this method. Typically an element will use the name
of the property it is bound to as name. As this name might already be
taken by another element (especially when lists of nested forms are used)
this method will append an integer value to the given name if necessary.