Adds advanced category
- advanced category hides less relevant configuration options
- omnitrace-avail has new '--advanced' option which shows these flags
- increase verbosity level to print issue with reading ppid children
- OMNITRACE_ROCTRACER_HSA_ACTIVITY defaults to ON
- OMNITRACE_ROCTRACER_HSA_API defaults to ON
* Remove reliance on MPI_Comm_rank
- read /proc/<PID>/tasks/<PID>/children of parent process to deduce the rank
- Old format relied on user calling MPI_Comm_rank(MPI_COMM_WORLD, ...)
- if MPI_Comm_rank called with subcommunicators only, multiple ranks would write to same file
* Tweak mpi example