sPuReMD: fix diagonal preconditioner computation and level scheduling application. Modify preconditioner logic to compute and cache sparsity-based info. Update run script.

Add minor checks to PG-PuReMD and PuReMD. Major refactoring of sPuReMD: backport much of PuReMD code and add CUSTOM geo format.

sPuReMD: fix SuperLU build and code. Fix ILU_PAR (compute factors separately). Move diagonal preconditioner computation. Refactor precondition computations. General code clean-up.