Fix RestApi url encode issue

"encodeQueryString" converts "%20" (space) to "+" which breaks Rest API
calls if the project name contains spaces. Fixed by using
"encodePathSegment" instead.

Change-Id: I049ca6ad54f36f36083222081c731325b5d51b95

gerrit-plugin-gwtui/src/main/java/com/google/gerrit/plugin/client/rpc/RestApi.java

@@ -37,7 +37,7 @@ public class RestApi {
   }
 
   public RestApi id(String id) {
-    return idRaw(URL.encodeQueryString(id));
+    return idRaw(URL.encodePathSegment(id));
   }
 
   public RestApi id(int id) {