Fix duplicate saving on quit

Slight refactor to split server stop and close functions
	Quit function explicitly sends SIGTERM
	SIGTERM doesn't trigger an os.Exit

	Bonus: Properly save the world on spawning the rover

cmd/rove/main_test.go

@@ -28,7 +28,7 @@ func TestMain(m *testing.M) {
 	fmt.Printf("Test server hosted on %s", address)
 	code := m.Run()
 
-	if err := s.Close(); err != nil {
+	if err := s.StopAndClose(); err != nil {
 		fmt.Println(err)
 		os.Exit(1)
 	}