Add support for Function and Trigger domain objects (#1060)

Vast commit, includes:

 * Introduces the Trigger domain entity.
 * Introduces the Fns domain entity.
 * V2 of the API for interacting with the new entities in swaggerv2.yml
 * Adds v2 end points for Apps to support PUT updates.
 * Rewrites the datastore level tests into a new pattern.
 * V2 routes use entity ID over name as the path parameter.

api/server/routes_list.go

@@ -19,7 +19,7 @@ func (s *Server) handleRouteList(c *gin.Context) {
 
 	routes, err := s.datastore.GetRoutesByApp(ctx, c.MustGet(api.AppID).(string), &filter)
 	if err != nil {
-		handleErrorResponse(c, err)
+		handleV1ErrorResponse(c, err)
 		return
 	}