Mapping engine arguments to parsnip arguments REDUX

[juliasilge]

In #321 we added tables to show which parsnip arguments correspond to which engine arguments, but they have since been removed. Now, our details pages like these show a translation but it isn't clear what argument corresponds to what.

Let's add something like those old tables back to the detail pages. (Maybe a model page? Not sure.)

[simonpcouch]

Looks like we lost that info in #456; would be great to restore. May be worth considering at the same time as #954.

[simonpcouch]

Ah, related to #725 as well.