Edge-based routing without turn-costs

[easbar]

Discussion came up in #1698.

[easbar]

I think ideally we would have:

• traversal_mode=edge_based/node_based (or edge_based=true/false ?) to determine the traversal mode, default: node. I think I would prefer traversal_mode, because this way we could throw an error if somebody still uses edge_based.
• turn_costs=true/false to enable/disable turn costs, default: false

Maybe we need to make the defaults for traversal_mode and turn_costs configurable via config.yml ?

case	traversal_mode	turn_costs	expected behavior
1	node_based	false	node-based routing, no turn costs (and no u-turns)
2	node_based	true	enable traversal_mode=edge_based automatically
3	edge_based	false	edge-based routing, no turn costs (u-turns are free) unless CH is enabled in this case this should be an error because there will only be an edge-based CH profile with turn costs !? (see below)
4	edge_based	true	edge-based routing with turn costs and default u-turn costs (infinity/no u-turns)

So from the user perspective the most common cases would be:

• specify nothing -> node based, no turn costs, no u-turns
• set turn_costs=true -> edge based, with turn costs, no u-turns

For expert users:

• set traversal_mode=edge_based -> edge-based routing, no turn costs, free u-turns

After this selection is made we check (do not use the vehicle or encoding manager to 'derive' the values for edge_based/turn_costs as is done currently):

• if turn_costs=true: does the selected vehicle/encoder support turn costs (i.e. is there a turn cost extension for this encoder) ? if not throw an error.
• is there a CH profile for the selected vehicle and the chosen traversal mode ? if not throw an error. however see If only edge based CH is prepared no error should be thrown #1637...
• if an edge-based CH profile is selected and turn_costs=false throw an error (or should this be possible as well (requires edge-based CH preparation without turn costs and keeping track if CH preparation included turn-costs or not (in CHProfile)).