Add option to display document structure by default

[camillem]

Is your feature request related to a problem? Please describe. I use more often than not the feature to display the structure of a document, so I have to enable it for every document of a collective.

Describe the solution you'd like It would be nice to be able to set a default value for each collective, in Parameters > Page parameters, alongside Default display mode.

Describe alternatives you've considered Currently doing it manually on every page.

Additional context This is similar to #1206

Thanks!