In interpretGlobalCoefficients, added guard against localID==-1, which can happen if some mapped coefficients aren't rank-local.  In such a case, we set the global coefficient to 0.  Not sure what else we could do.  I think this is reasonable, but I'm not dead certain of it..
Removed some file I/O from GDAMinimumRuleTests.
Commented out some lines that would output vectors and matrices to disk.
Added relative tolerance, and a minimum tolerance for CG iteration.
PoissonGMGDriver.