Introduce SAVEPOINT and CHECKPOINT storage reasons
Introduce SAVEPOINT and CHECKPOINT storage reasons


Former-commit-id: 9ccb8ad3522b1c718ce6297b2f8d843b36d24f05
DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG