The preceding version picker should propose and accept only a restricted list of pages

Implemented using a customer displayer and picker.
The 3 following restrictions have been implemented:

• coming from the current book,
• that are actual version pages,
• not the currently edited version,

This restriction has not been implemented

"and avoid loops (if V4 inherits from V3, and V3 from V2, V2 shouldn't be able to inherit from V4)"
Issue BVERSION-72 has been created for it

It's currently the responsibility of the editor to not create loops of versions.

Implemented