Add developer Getting Started guide

First cut at the developer getting started guide.

Intended to replace:
- https://github.com/ManageIQ/cfme/wiki/Developer-Setup
- other private getting started docs
What parts of this line can the person running it customize to what they want?  For example, is "secret" the actual password you want them to use? or can they use whatever password they want?  If it's whatever password they want, then make it "whateverpasswordyouwant or something like that.