Simplify and improve Topology interface (#3579)

* Hide function

* Revert

* Fix facets

* Simplify

* Simplify

* Add hack

* Move hack

* Simplifications

* Simplify

* Test update

* Simplify

* Doc fix

* Remove old code

* Interface update

* Doc updates

* Doc fix

* Simplify constructor.

* Fix key

* Remove interfaces

* Remove old code

* Remove constructor

* Doc improvements

* Doc fix