Bug fixes

* Error page with relevant error message in case of missing stages/jobs

Before:
![screen shot 2014-11-03 at 10 34 17](https://cloud.githubusercontent.com/assets/1046342/4878784/63b52cc2-6318-11e4-9048-87b69e484e23.png)

After:
![screen shot 2014-11-03 at 10 34 58](https://cloud.githubusercontent.com/assets/1046342/4878788/7b294352-6318-11e4-8496-118e3411674c.png)


* Layout was being rendered multiple times in case of config merge error scenarios, fixed that. Also, the reload button works now.

Before:
![screen shot 2014-11-03 at 10 40 09](https://cloud.githubusercontent.com/assets/1046342/4878791/84d95b8a-6318-11e4-8a97-fcc902d87e60.png)


After: (Currently the error message is partially hidden by the page_header, this needs some css fix - need help.)
![screen shot 2014-11-03 at 10 41 07](https://cloud.githubusercontent.com/assets/1046342/4878794/8be28848-6318-11e4-93e8-bb4732949ac5.png)