Node cost calculation is arbitrary and obscure

[heijul]

There are a few issues with how the node costs are calculated.

1. First and foremost, the function currently used, is arbitrary at best.
   (Currently uses (route_type_score + node_has_this_many_optional_values) ** 2 // 20)

2. We should also change where the node costs are calculated, instead of doing something like this.

In other words, we probably need to

• Move everything node cost related to a single place
• Find a function that has some fixed limit and increases fast for smaller values. (log?)
  It should also take the optional values into account, though it should not increase linearly based on them.
• Document how the function works and why it is a good function
• Test it