WIP: clean-up DataType and add Last back
This MR is needed for my WIP attempt to resurrect TupleToolCaloHypo:
- add Last DataType to facilitate a loop over all DataType variables
- change
enum class
toenum
so DataType objects can be directly compared to int in the loop
I am afraid these changes are a step back in the optimisation of DataType and would happy to receive suggestions on how to loop over all the DataType variables in a different way that don't requires them.
Since I was there I've also cleaned-up the SPD/PS related variables.