Adderrata

Hello liweinan,

As per dcheung's request, I have added an "Add to Errata" button that will send an http request to the Errata server, if the build's status is 'Finished'. The request sends a list of bugzilla bug Ids, and the mead name of the pack.

The API docs for sending the Errata request are not available yet, so I have written comments where we will need to make changes once we know the details for that http request. For example, we don't have the Errata server's URI and resource path, or what error codes/messages we can expect to receive if something is incorrect with the request. So maybe it's best to wait until those details are available before merging these changes.

Here is a screenshot:
![adderrata](https://f.cloud.github.com/assets/1285582/863019/5f2ac5c6-f600-11e2-96ee-4bce6dc0711b.png)

thanks,
francisco