tests.sh: support absolute path to outdir

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests.sh: remove --quiet option on calls to time

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests.sh: add -node option

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests.sh: allow errlist file inside outdir

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
tests.sh: add env var to move xml file

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>
src: intro nitest a tester of Nit engines using MPI

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>