Mostly doc changes and some bug fixes

Use render() instead of a local wikifier, making it possible to render DOM directly in special passages

Fixes #1704.

This reverts merge request !5960

Teach SugarCube to avoid cloning the state object when history size is
equal to 1

Define save descriptions uniformly for the entire game, instead of using nonsense everywhere that's not the main page.
Patch Sugarcube to skip creating passage excerpts (which can be expensive) when descriptions are predefined.

This reverts merge request !4969