Config rework

[caliban0]

Resolves #29.

[zalmarge]

Please change the first two sentences in the output of cherryctl help to:

Init will prompt for account settings and store the values as defaults in a configuration file.
This file is stored in the default user configuration directory (platform dependent), unless otherwise specified by the --config flag.

Ran the checks manually, the functionality itself is fine. Good job!

[caliban0]

Done.