Chef recipe

Improve the integration with Chef.
The new recipe don't force to get chef url from the globaal context (so the inherited recipe can provide this url by another way, it is usefull if we don't rely on a chef server deployed by cloudify)
The new recipe save runParams in the context. And we restore it in case of self-healing).
We add a custom command named 'rerun' that re-execute the chef-client, useful after an update of the runParams.