Adjust paths and costs in Pathfinder.
Update SQLite to 3.8.7:
sha1: 3e23079f062fc06705eead4db108ee429878b532
Clean up Pathfinder.

* Restrict to 80-columns and other style cleanups.
* Make pathfinding a free function and hide the class Pathfinder.
* Split off unrelated utility functions into separate files.
Fix pathfinding with multiple issuers for one currency (RIPD-618).