Rewrite PtRouter

[hcourt]

Okay so we need to rewrite the PtRouter.

Tasks:

• [x] Pseudocode what's there now
• [ ] Pseudocode what we want (below)
• [ ] Do it in Java

Major changes:

• Transit edges need weights, just like bike edges. These should be roughly the same magnitude as bike edges so we can compare them
• Keep Dijkstra's, but use weights instead of time for edge selection.
• Still keep around edge time for filtering out transit edges with departure times that are too early or in the past.
• Add tuneable knobs for:
  • Transit weight/bike weight ratio
  • Transit weight between mode, time, number of transfers

[hcourt]

We think we want to rewrite PtRouterImpl.RequestHandler.findPaths to use a single Dijkstra's pass instead of multiple passes with reversing; and rewrite MultiCriteriaLabelSetting/GraphExplorer to use weight instead of time.

[abhumbla]

i think a goal of this task should be to make the PT router not a special case in the config, but an actual profile with its own parameters (different types of weighting could be one). this could help a lot of weirdness we get interacting with the PT endpoints vs the normal one

at the extreme end of this we would unify PT graph and street graph and use the same graph algorithms (just that PT profile also needs to keep track of the current time). but for now i think just making it a first-class profile will have a lot of benefits