[WIP] Add CHANGELOG.md with work from Sprint 12

@ManageIQ/core Please review

I'm taking a cue from http://keepachangelog.com and getting a change log into our repository based on the results from the [last sprint](https://github.com/ManageIQ/manageiq/issues?q=milestone%3A%22Sprint+12+-+Sept+9%2C+2014%22).  After the demo planning meeting this morning, I've taken the highlights from that, and put them into the change log as what was "Added".  However, there is still a little more to do before merging...

- Give a little more detail on the automate model changes (@gmcculloug @tinaafitz @mkanoor)
- Highlight the "major" bug fixes.

Any help you can give is appreciated.
Ability to generate encryption keys through the appliance console and cli.
Ability to generate postgres certificates leveraging IPA in the appliance console cli.