Common solver options should be output by --help

[PerMildner]

minizinc --help outputs no solver options, not even those for the chosen (explicitly or by default) solver.

This makes them hard to discover. (In my case I did not know about --solver-statistics and used --statistics which also enables (chatty #705) compiler statistics.)

Especially the common solver options would be nice to have, but an alternative would be to always pass --help to the chosen solver.