Add middleware initialisation points to app property information

Details of the app's environment are updated to include initialisation points of the middleware stack as seen at `/rails/info/properties`.  This is particularly handy when developing engines etc.

Tested on a Rails 4.0.0.beta app.

![Screen Shot 2013-01-26 at 02 28 43](https://f.cloud.github.com/assets/368260/98802/1c0736d6-6734-11e2-8e8e-1181e997c69a.png)