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_delete.go

@@ -15,12 +15,12 @@ func (s *Server) handleRouteDelete(c *gin.Context) {
 	routePath := path.Clean(c.MustGet(api.Path).(string))
 
 	if _, err := s.datastore.GetRoute(ctx, appID, routePath); err != nil {
-		handleErrorResponse(c, err)
+		handleV1ErrorResponse(c, err)
 		return
 	}
 
 	if err := s.datastore.RemoveRoute(ctx, appID, routePath); err != nil {
-		handleErrorResponse(c, err)
+		handleV1ErrorResponse(c, err)
 		return
 	}