add OGS_USE_MPI cmake option and USE_MPI macro
add Logog Cout which allows one computing core (rank 0) to print the log
add padLeft() to StringTools
print MPI rank to logog output
extend LogogCustomCout to support level dependent output
configure MPI in CMake
Merge pull request #510 from norihiro-w/log-MPI

Logog target for MPI computation