OT t0 time tools provoke FP auditor into crashing

Gaudi::Math::ValueWithError's constructor and error methods are not transparent to quiet NaNs, since they do arithmetic on the constructor's arguments. Until we've figured out a good way to deal with that that impacts nobody else, we change the type returned by the OT track t0 tools (with a type alias) to something much simpler that is transparent to NaNs. Fix one place where a NaN produced by the OT track t0 tools confused the packing, while we're at it.

changed target branch from 2016-patches to run2-patches

Please note that this depends on Rec!1525 (merged)

unmarked as a Work In Progress

• [2019-05-07 00:14] Validation started with lhcb-run2-patches#380

@erodrigu I am happy to merge this

mentioned in commit 7ebe4d2f

merged