Allow selectable component to overwrite shape of displayed selection from footprint

[wowgetoffyourcellphone]

How do we use this?  

https://code.wildfiregames.com/D2844

https://trac.wildfiregames.com/changeset/23900

[Silier]

<Selectable>
    <Overlay>
      <Shape>
		<Square width="3" depth="6"/>
      </Shape>
      <Texture>
        <MainTexture>128x256/ellipse.png</MainTexture>
        <MainTextureMask>128x256/ellipse_mask.png</MainTextureMask>
      </Texture>
    </Overlay>
  </Selectable>

Or <Circle radius="1.5"/>