Type-2 aggregation (multi-message, multi-slot)

[TomWambsgans]

Goal:

• allow arbitrary (recursive) aggregation on single-message + single-slot. You can basically merge with duplicates, remove -> total freedom. Call it type-1.
• allow "merging" an arbitrary number n of type-1 multi-signatures into a multi-signatures for n pairs (message, slot). Call it type-2.
• allow "splitting" a type-2 multi-signature back into n independent type-1 signatures.