0.5 Docs. Populate local installer repo.

Addition of content from mailing list.

Command (and explanation) to prefetch the content's of Cloudsoft's fallback repository to  `~/.brooklyn/repository`.

Footnotes?

---

![Screen shot 2013-04-25 at 12 16 59](https://f.cloud.github.com/assets/879000/424868/b5d20dd0-ad99-11e2-8b21-1c4f4a527912.png)