Temporarily disable Events/Batches in UrQMD.
Clarify UrQMD particle dictionary.
Convert UrQMD class to a generator [simpler + faster].
Remove defined MCID function:  it was only called once.  Also marginally faster.
Simplify particle IDs variable name.
Ignore particle/antiparticle when filtering IDs.
Replace old event reader.  Add particle filtering.