Introduce RotateEngine and Rct2Engine, FixedSeedSequence and Rct2Seed.
Adhere respectively to requirements `RandomNumberEngine` and `SeedSequence`.
Can be used with C++11 adaptors and distributions in <random>.
It turns out that trying to just give a peep a pathfinding goal and then let them loose doesn't work, because every time they reach a junction, the pathfinder has them walk 'aimlessly' instead of pursuing their target. That's why we were seeing some very large step counts in previous tests - they were (eventually) walking onto the target square, but only after lots of wandering around in circles.
This commit reworks the test data to contain an actual ride for each test scenario, where the peep will path to the tile in front of the ride entrance. A nice side benefit of this is that the ride names must match the test names, so you can now tell from looking at the rides in the test data which one is used for which test instance.
The 'yellow marker' tiles for goal positions are also removed here, as we're deriving goal positions from the ride entrances instead.
To make it a little clearer what the parameter is for, rename FindPath::maxSteps to FindPath::expectedSteps, and extend the comment to describe what happens in negative test scenarios.
There exists a helper function map_get_surface_element_at which already searches a tile's element list for the surface element, so we can just use that.
