Login/logout buttons with basic account manager

Currently this checks to see if a user is logged in by hitting the XHR
endpoint /accounts/self/detail upon initial page load.

Change-Id: Ida77c60bf9fee34ddfaee85a15b68cdf85a58af7
Feature: Issue 3693
diff --git a/polygerrit-ui/server.go b/polygerrit-ui/server.go
index 008fe1d..29b81f4 100644
--- a/polygerrit-ui/server.go
+++ b/polygerrit-ui/server.go
@@ -68,6 +68,7 @@
 		return
 	}
 	defer res.Body.Close()
+	w.WriteHeader(res.StatusCode)
 	if _, err := io.Copy(w, res.Body); err != nil {
 		log.Println("Error copying response to ResponseWriter:", err)
 		return