Classifications for same patient/sample

I would like a box on the classification page that summarises other classifications for the same patient/sample

Shariant team needs to discuss whether they want to enable this.

* In VG - we link classification to sample, and thus can group by this, or ```sample.patient``` (or both). People don't always link on this, so we could also use sample_id (so long as lab.external=False)

* In Shariant, we could perhaps group by lab/sample_id