Update and document pe_bootstrap provisioner model

The model was not setting a couple of attributes in the `to_proc` method,
notably `master`. YARD documentation also updated with material from the
README.
Update documentation of global model

YARD documentation for pe_builder global configu_builder model has been updated
to match what is described in the README.
Merge pull request #27 from Sharpie/update-config-builder-model

Update config builder models