Modify testing map

Make map used for tests a bit interesting (adjust all dependant tests)
Improve pathfinding tests

Check if string representation of found patch matches expected value instead of previous checking for path equality (seems to be more understandable now what is happening)
Finalize pathfinding

Previous version was able to fond path only to junction, now it is able to find path to any rail
Small refactorings

has_rail->has_junction
improve PathSet tests