Add vegas_hpc_server

The program looks for START, STOP or QUIT messages on /tmp/vegas_hpc_command (a FIFO) to launch processing threads.

Uses the OBS_MODE parameter to determine if mode should be HBW or LBW. This may clash with GUPPI's style, so perhaps we should change to VEGAS_MODE.

Only tested OBS_MODE=HBW so far, seems to work.

Also updated vegas_set_params and setup_shmem_mode01 to ensure OBS_MODE gets set (HBW by default)