Remove parallelization in surf.

Signed-off-by: Guillaume Serrière <guillaume.serriere@esial.net>
Add context creation for worker in parmap.

Signed-off-by: Guillaume Serrière <guillaume.serriere@esial.net>
Add tracefile for runall.

This file will store couple (nbprocesses,time_ellapse) for every call of runall (serial or parallel).
Signed-off-by: Guillaume Serrière <guillaume.serriere@esial.net>