Added RuntimeMPI::AllGather

- Moved injectMockData fram test code to mpiutils.
- Added mpiutils::dumpArray for help with debugging.
- Added test for allGather
Updated examples to compile with the new organization of include dirs
and namespaces.
Expanded and cleaned up mpi-test basicCalculator.
Added basis mpi-calculator example that will be used to benchmark MPI.
Added PrintMPIBackendASTVisitor to compiler.

- PrintCPUBackendASTVisitor now has a couple of virtual methods for
overriding the header and footer of the generated source.
- The option to ec for selecting the backend has been updated with a new
enum for the MPI backend.
Exports ${Zoltan_INCLUDE_DIRS} into ${EQUELLE_INCLUDE_DIRS_FOR_CONFIG}.

- This is needed for generated programs to compile with RuntimeMPI.
Change order of link-libraries when exporting EQUELLE_LIBS_FOR_CONFIG in
MPI backend.
Added RuntimeMPI::output
PrintMPIBackendASTVisitor::cppStartString so that it initializes MPI and
decomposes the grid.
Added minor example to demonstrate the full pipeline of generated MPI-