TauAnalysisTools and DFTau: introduce read/write decor handles for derivations in MT

Hello,

This MR is replacing accessors/decorators with Read/WriteDecorHandles in TauAnalysisTools and DerivationFrameworkTau, which will be necessary to run derivations in MT. This addresses an issue seen when running DAODs in MT (ATLASG-2470):

08:03:01 ToolSvc.TauSelectorLoose                              15     0 WARNING SG::ExcBadAuxVar: Attempt to retrieve nonexistent aux data item `::EleRNNLoose_v1' (946).

where a TauSelectionTool was trying to read a decoration before it was created by TauIDDecoratorWrapper.

The downside is that now, a tau container name must be declared in TauSelectionTool, while before, any TauJet object could be passed regardless of the tau container it came from (but now we can't avoid that).

Tagging @ademaria .

Cheers, Bertrand