Persistent commercial ab test

This sets up a persistent ab test, for the commercial component. As we're sending the ab test segment to DFP, they can now use that as a targeting hook, e.g. show a different component if they're in the test or not

So not a true ab test, but allows us to get the benefits of it, i.e. remember what test you're in, pass the segment on to omniture, etc 
need to run ab segmentation, etc here as both `commercial` and `app` bootstraps needs it

`ab.js` is bundled in `core.js`, so no extra requests