Don't flatten modules with multiple types

[Gama11]

They should have their own entry in the navigation and their own pages that list all the types they contain.

The trickiest part would probably be how to deal with the filter textbox, since it's probably more convenient to keep everything flattened there?

[nadako]

If/when this is done, it should as well list haxe 4.2 module-statics (hopefully the xml output has enough info for this).

Also it would be nice to generate a page for the module with the list of its contents.

[nanjizal]

dox support would be amazing, I am already using this on my libraries but would prevent putting them on haxelib.
note currently the changes are breaking testing when using haxe-doctest, I have not yet looked into why, but would be good if the default haxe-doctest test were added to release tests.