Muelu: Allow to change distributor options
Created by: cgcgcg
@trilinos/muelu @trilinos/xpetra
Description
This PR adds the option to set a new sublist "matvec params" in the xml interface. The content of the sublist will be applied to the underlying Tpetra::Distributors for the solve phase. In particular, this allows to choose different communication options apart from the default Irecv-Send pattern.