Have edit links for dynamically-generated documentation pages point to their source files

[dylanhmorris]

This is possible. See for example here:

https://github.com/vispy/vispy/blob/6855a9c6ab1058e290d7bdfdce83551c5b18c343/doc/conf.py#L138-L180

It will eliminate the need for placeholder files and associated hooks.