It holds necessary state plus additional information relative to the
context which we are being run to (e.g. if we are in a terminal or not).
Besides in the future we can use it also as a contextual logger to
provide more smart logging capabilities.
This also replace the general global configuration instance that
previously was share between the core components.
Contact the notary server if ```--verify``` is specified (or `verify:
true` is enabled on the repo config) and verify if the image is signed,
use the returned value to pull the verified image.
