The former has been formally deprecated for a long time and in CUDA 10.0
it is finally properly marked as deprecated, so the compiler can print
warnings.

It has not been implemented in the past decade so it can be safely
assumed that it is useless.

Fixed handling of the boundary conditions for explicit solver - introduced a method Problem::applyBoundaryConditions.

Preapare Distributed Grids for Communication groups (aka MPI Communicator)

Why do problems have this method anyway? It was obviously never used...

Added parallel reduction to communicators.

Implemeting heat equation benchmark.

Fixing the solvers.