documentation/python: robust linking also for nested/generic types.

documentation/python: robust linking also for nested/generic types.

Wow of course this again took me ten times more than originally
anticipated, because there are NO FREAKING DOCS AT ALL for the typing
module.

The major advantage of the new (hard to implement) approach is that
string annotations are parsed and dereferenced correctly as well. That
also means the previous way I did them (fully qualified names) was
mostly wrong.