Write a Readme for the cdk framework

[bdemann]

We need to have a simple Readme to help users and contributors understand how the cdk_framework works. Essentially distill Ben's knowledge into the Readme so when we comeback to it in six months we still understand what on earth he was thinking

[bdemann]

For the README
There are two kinds of things we want to pass in as the parental prefix, either the name of the parent, or the name that we want the thing to take on if it's inline. That's it. So if it asks for a parent's name give that, if it asks for a name, give that.