Second version of jobs in YAML:

Create a 'seed' job which:
- is triggered by github
- defines its repository on github
- clones buildout.coredev repo and runs buildout on it
- archives buildout.coredev so that it can be used on downstream projects
- triggers downstream jobs

Create a 'package tests' job which:
- clones buildout.coredev from upstream 'seed' job
- runs tests on the package
- publishes unittest results, sends emails on errors and also publishes robot reports
Add docs for each YAML section