Do not specify slave program name twice when launching slave process

Open MPI does not support output redirection for spawned child
processes.

Copy command line parameters from master to slave command line. Also
replace data file name in master argv with data file name of the slave.

Remove debug code that was introduced by mistake in the previous commit

Create one log file for each slave subprocess. Redirect both
stdout and stderr to this file

Exclude the reservoir coupling stuff if MPI is not enabled