v0.11.0: Valhalla support

• Nigiri based re-implementation of endpoints used by the web user interface
• Valhalla module wrapping the Valhalla street routing

What's Changed

• valhalla router as alternative to ppr/osrm by @felixguendling in #360
• nigiri guesser by @felixguendling in #361
• nigiri railviz by @felixguendling in #363
• fix nigiri railviz overlap check by @felixguendling in #365
• nigiri: fix railviz for block_id trips by @felixguendling in #366
• station lookup by @felixguendling in #367

Full Changelog: v0.10.2...v0.11.0