@Trilinos/MueLu Geometric Multigrid implementation in GeneralGeometricPFactory with helper coordinatesTransferFactory

Created by: lucbv

@jhux2 @tawiesn @rstumin Here is the finally ready, Geometric Multigrid algorithm, I think that I performed the git pull --rebase and push correctly and it seems that my repository: lucbv/Trilinos is well synced with trilinos/Trilinos at the time of my push so this should make things easy for everyone. At the moment I focused on the serial implementation and I did not look into the GO at all since I figured that serial simulations would not require it. However I plan on adding it in the next push for the parallel version. The assumption of the same number of nodes in each direction is made on purpose, as I am still not 100% sure of all the assumptions that we will make to detect the number of nodes per directions.

I am attaching an xml file that I use with muelu/test/scaling/Driver.cpp to run LaplaceND and ElasticityND problems. gmg_xml.pdf

Let me know if there are any changes and mistake that need to be fixed.