Add information about using the recommended initial solution

[JakubKudela89]

The "recommended" initial solutions (all zeros for bbob, feasible solution for bbob-constrained,..) can be quite advantageous in some situations (particularly in higher dimensions). This information should appear somewhere in the description of how to run the experiments.

[brockho]

Agreed. To precise: we took care of this, for sure, in python but likely forgot to update the example experiments in other languages...