fix pick_version (avoid crashes when no less recent versions are available);...

fix pick_version (avoid crashes when no less recent versions are available); take a deep copy of the specifications passed to select_or_generate_ec such that it doesn't get updated on the caller's end; make match check stricter, also take into account parameters that are not set in selected easyconfig; correct updating of toolkit with specified version; mention old version in comment for tweaked parameter values