Fix cli for structopt 0.3.7 and pin to that version (#4509)

* Fix cli for structopt 0.3.7 and pin to that version

This is just some hotfix to make everything compile. In the future it
will require another pr to not depend on internals of StructOpt, but
that will probably also require some additions to StructOpt itself. To
not break the code again with another StructOpt, this also pins the
StructOpt version.

* Fix benches

* Fix for fix