Prompt users to select from recommended ezbake templates

[abd3]

Running ezbake prepare should prompt the user to choose from one of several recommended default ezbake templates (provided by Appirio Digital and AppirioDX), or allow users to choose "other" and then provide the URL to an ezbake template.

There could be a global configuration setting that points to a different set of "common" ezbake ingredients, so that this module could remain generic but Appirio folks could have a more opinionated set of scaffolding steps.