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.

test/fn-system-tests/system_test.go

@@ -34,10 +34,6 @@ const (
 	LBAddress = "http://127.0.0.1:8081"
 )
 
-type SystemTestNodePool struct {
-	runners []pool.Runner
-}
-
 func LB() (string, error) {
 	u, err := url.Parse(LBAddress)
 	if err != nil {