Added StokesVGPFormulation.
Hardened the ZMC and point-constraint tests to compare the pressure solution, too.  Still pass.
Excised some "using namespace" lines from header files.
Added build directives for StokesCavityFlowDriverForPaper.
Added declaration for mumpsMaxMemoryMB.
Various tweaks for StokesCavityFlowDriverGMGExperiment.