spell sdk, developer happiness

[battlemidget]

We need to decide on the best course of action for some sort of spell sdk. The reactive pattern looks like a great candidate for something like this (borrowing the ideas from charms.reactive). This would give us both bash and python bindings initially.

An example thought of how 00-deploy_done could work:

@when_ready
def all_apps_started():
    success('All applications started')

This is a brainstorming issue to attempt to settle on the way forward for spell development.

@mikemccracken @marcoceppi