Tweaked the way energy error is computed, and gave access to the stored history of energy error, dof count, and element count.
Commented out some console output.
A bunch of effort toward GMG preconditioner, including tests and additive Schwarz option.
Added Stokes formulation without an explicit pressure variable.
Tweaks to drivers for GMG preconditioner.
Added prototype refinement strategy that guarantees refinement of cells representing a certain total percentage of the error. Largely untested and unused at this point.
Added prototype IPFilter, which allows the definition of a LocalStiffnessMatrixFilter via a trial-space IP object.  Notion is that you might want to minimize (e_i, e_j)_E + (e_i, e_j)_ip, where E is the energy norm, and _ip is the inner product defined by the IP object.  Could be used for resolution of the extra constant mode in Stokes operator, e.g., if _ip were defined as (p,p)_L^2, say.