Updated the build instructions for the examples.
Renamed binary zoltanIntegration_test -> RuntimeMPI_test.
Added RuntimeMPI::insterScalarWithDefault.
Implemented RuntimeMPI::boundaryCells

- Added convenience method SubGrid::map_to_global to faciliatet testing.
Better handling of inner and outer boundaries.

- Boundary enum is moved from ZoltanGrid.hpp to equelleTypes.hpp.
- EquelleRuntimeCPU::isBoundary now checks for boundary::outer and not >
0.
Added RuntimeMPI::boundaryFaces.