Add --output-path option to cloe-engine

[CzBalti]

[cassava]

I pushed a fix-up with my suggested changes. If you are fine with that, rebase and fixup the two commits into a single one.

[cassava]

I rebased on ben/develop, so you'll have to reset to your origin.

[CzBalti]

Do we need to write tests for this?

[cassava]

Do we need to write tests for this?

Let's write a system test. Should be pretty straightforward.