To tidy up __call__ in RouteLayer.

The test

TestRouteLayer::test_query_with_no_index

was failing because when it ran

assert route_layer("Anything").name is None

There were no Routes defined yet, and this meant that

route = [route for route in self.routes if route.name == top_class][0] was raising an error.

If no routes are defined then we can just defualt to RouteChoice().

Created a random_score_threshold_search method in TestRouteSelection for finding optimum score threshold values across all routes, using a random search algorithm.

Also created a fit method in RouteLayer for running the random_score_threshold_search and for

User inputted value was being overruled by hardcoded list.