Improve detection of mozart install

[layus]

At the moment we expect "ozengine" to reside in the path.

We could try harder to find mozart2 in the user system. An propose to install it ourselves if it is not up-to-date, or not installed.

[SuperLanceur]

The path will most likely be /Applications/Mozart2.app/Contents/Resources/bin/ozengine on macOS systems. I'll look for default locations on other OSes and draft a PR.