Rename OSMHandler phase handler to ease reading.
Make Area, AreaGroup and Ring first class citizens.

OpenStreetMapGraphBuilder is already way too big,
no need to add unnecessary inner classes.
Split OpenStreetMapGraphBuilder in 4 classes.
Remove warning.
Rename OSM index fields, add comments.
Move unify turn restriction stuff to own function.
Move walkable area builder to dedicated class.

This change is meant to be temporary, until the building
process is refactored. The code is not optimal.
Set way name for areas.
Dedicated method to test for bike rental nodes.
Removed unused code.
Remove deprecated TODO.
Replace comment at the correct place.
Add method to insert a node into a way.
Fix #1562 - handle intersecting unconnected P+R.
Rename side-effect method to apply, not get.
Move single way area processing to own function.
Handle multi-polygon P+R.
Add unconnected P+R areas unit-test (#1562).
Add TODO in unique strange function.
Add toString to OSMRelationMember. Format code.