Added a draft implementation of new Solution data gather/scatter.  Does NOT pass tests when running on 4 MPI nodes.
Added ability to get descendent cellIDs for Element.
A few minor bug fixes for Mesh, plus a new MeshGeometry constructor that doesn't need an edgeToCurveMap.
MPI-enabled maxConditionNumber determination.
Fixed IncompressibleFormulationsTests to call new condensed solve version of iterate().
Tweaks to NavierStokesCavityFlowDriver.
Messing around with NavierStokesHemkerDriver.  I'm pretty sure things are NOT working right now, though they were once upon a time (my stream function looks different for Re 40, say).  Unclear what's wrong; might be worth going through the git history...
Messing around with StokesCavityFlowDriver.