Refactor task chain up to limits
This PR refactors the task chain to create limit plots. Most important changes:
- Added
MultiDatacardBaseTask
,POITask1DWithR
andPOIScanTask1DWithR
- Encoded hash of input datacards into output paths
- Added two new plots (
PlotMultipleUpperLimits
,PlotUpperLimitsAtPOI
) for comparing limits across configurations - Updated docs accordingly