fix t2t vit having two layernorms, and make final layernorm in distil…

…lation wrapper configurable, default to False for vit

rotary needs to be done with full precision to be safe

address #300

address #306

address #304

address #292

share an idea that should be tried if it has not been

allow channels to be customizable for cvt

no longer needed with einops 0.7