Improved saturation criterion
Improved saturation criterion

- Find plateau using a running standard deviation
- Compute slope on that plateau


Former-commit-id: d6ef2e89dc084cc9f1565baea91226aed42d053c
DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG,DavidAce/DMRG