Print contextual info on failure

[shaunsmith]

When the CLI fails to communicate with the server or with a repository or gets an error response code it would be useful to dump contextual info to remind the user of the current config, perhaps only when --verbose mode is enabled. This would be helpful when users have changed contexts or repositories and commands are failing. Useful contextual information could include:

• docker userid (who is the user logged in as?)
• value of FN_REGISTRY
• name of the current context
• any context refining provider specific values, like a profile name