Refactor GraphHopper class

Requirements:

* avoid inheritance
* avoid mutability
* better extension possibilities (no inheritance needed, see proposal)
* better support public transit use case
* separate reader and writer to easier support two scenarios of 1. create and query and 2. load and query
* allow to add CH/LM profiles even after import (no need for upfront config)
* simpler LM/CHPreparationHandler
* view storage not as cache but more as database and also be able to load config from this database?

First proposal: https://github.com/graphhopper/graphhopper/compare/experiment_gh_class

Related: #1492