Use of type_index for LoopAction type discovery
When sending to remote machines we can't rely on std::type_index having the same representation.
This is a problem for LoopActionBase::type (and c another issue).
In LoopAction the type is mostly used to decide how to build histograms:
- Events from one cycle of a trigger loop go into the same bin
- Events from one cycle of a mask loop go into the same bin
- Events from each step of a threshold loop go into different
- Something else?
Also some discussion here: atlas-itk/sw/itksw-design#1