Agg pipeline queries for all removable proofs when making a new degree proof
Adding degree proof should mark inactive if no removable proofs / downstream proofs from own are active
Adding a degree proof will delete own old proof if no dependents or all downstream proofs are inactive
Adding a degree proof will delete as many inactive upstream proofs as it can, including downstream on a different path if sharing common path
(i.e. if bob and charlie both know alice, and slice and charlie's proofs are inactive, bob will remove all 3 proofs on submission of their own proofs) (functionally charlie's proof wouldn't ever be there but the logic allows for it)
Addresses #76