Basic badge sharing and privacy control

This adds the following text to the top of `/mybadges` badge details pages for >13:

<img src="http://f.cl.ly/items/342h1X3m0Y1H2s441W2Q/13.png">
<img src="http://f.cl.ly/items/0W1S0D0P0p1q0m2S2T0l/13.png">

And adds this share page layout at that public url:

<img src="http://f.cl.ly/items/2w183B3U1O2U041y1B17/13.png">