move everything from c3nav.routing.graph to c3nav.routing

src/c3nav/routing/connection.py

@@ -0,0 +1,15 @@
+import numpy as np
+
+
+class GraphConnection():
+    def __init__(self, graph, from_point, to_point, distance=None):
+        self.graph = graph
+        self.from_point = from_point
+        self.to_point = to_point
+        self.distance = distance if distance is not None else np.linalg.norm(from_point.xy - to_point.xy)
+
+        if to_point in from_point.connections:
+            self.graph.connections.remove(from_point.connections[to_point])
+
+        from_point.connections[to_point] = self
+        to_point.connections_in[from_point] = self