env: status page

Updates page asynchronously every 5 seconds.
Introduces beforeStart and afterStart trigger points to update setup status information.

Change-Id: Ic2f6a9bb7a0fefeefc4d6a1a7338d506a4f99e80
diff --git a/core/installer/tasks/infra.go b/core/installer/tasks/infra.go
index 0685a6d..39a1cd5 100644
--- a/core/installer/tasks/infra.go
+++ b/core/installer/tasks/infra.go
@@ -30,6 +30,9 @@
 		st.emptySuffixGen = installer.NewEmptySuffixGenerator()
 		return nil
 	})
+	t.beforeStart = func() {
+		st.infoListener("Setting up core infrastructure services.")
+	}
 	return &t
 }