More efficient block lattices

[AidanMcDonald]

Blocks with more component multiplicities than 1 and N are currently handled in a sub-optimal way by treating components as complex regions with many surfaces. It's better to define the block as a lattice with a small number of different universes. The necessary information is present in the blueprints input file as latticeIDs and lattice maps, but I so far haven't found this information inside the ARMI reactor.core object. I need to either find latticeIDs inside the core object or re-read the blueprints file when necessary.