Adding hooks to tau sequence to read from DB

* restoring PhysicsTFormulaPayload and PhysicsTGraphPayload plugins deleted in earlier release
* adding interfaces to tau MVA discriminators to be able to read also from the sqlite
* adding a master python switch that makes all relevant discriminators read from sqlite instead of local root file

These pre-requsites are necessary for the tau payloads to be moved to CondDB. This PR does not change default RECO at all, only adds possibility to run with different input that is turned off by default.
What is the expected effect of this change?