mpiInfo: fix broken CMakeFile

- LINK_DIRECTORIES causes problems on taurus and is NOT
  necessary at all
  http://cmake.org/cmake/help/v2.8.11/cmake.html#command:link_directories
- general clean-up
BullXMPI / FindMPI fix

- at least for mpiInfo, Bullxmpi tries to link against the
  deprecated MPI C++ Interfaces (whyyyyy?)
- since it is hard to find what depencency resolves the same
  problem in PIConGPU, we add the same work-around here
- another option: it would be possible to use the FindMPI
  deprecated var MPI_LIBRARIES instead, but we avoid that
Fix ELSEIF -> ELSE mismatch

- messages for splash and pngwriter not found
- fix bug introduced with 8e4609e06ef258cb08a646e665131e65b26cd3b5