Added support for materializing Generic instances for product types such that the representation type is known to be an HList.
Added support for materializing Generic instances for product types such that the representation type is known to be an HList.

TomasMikula/shapeless,malcolmgreaves/shapeless,milessabin/shapeless,roberth/shapeless,liff/shapeless,clhodapp/shapeless,alexarchambault/shapeless,fthomas/shapeless,joescii/shapeless,tek/shapeless,wheaties/shapeless,Atry/shapeless,triggerNZ/shapeless,khronnuz/shapeless,lukasz-golebiewski/shapeless,isaka/shapeless,lambdista/shapeless,notxcain/shapeless