Persist template, shifts, and heuristic together
Persist template, shifts, and heuristic together

Instead of having `persist` called at various points during graph
construction in image registration, wait until after the graph is fully
constructed and call `persist` once on all relevant values needed for
the next iteration. This should help better separate graph construction
from computation. Also this should give distributed a better idea of
what needs to be computed and kept so that it can better plan the
computation and keep the relevant results.

DudLab/nanshe_workflow,nanshe-org/nanshe_workflow