Don't add any extra space to RadioButton and CheckBox by default

We instead do this in the layout code. It seems to make sense to support
the use case where only the indicator is visible without adding
extra padding to it.

Change-Id: Ib55c3a97d7c23a52a14121b46be84299d1ad2132
Reviewed-by: J-P Nurmi <jpnurmi@digia.com>