Add minid 'config' command

[NickolausDS]

Add a CLI 'config' command for changing some general runtime behaviors of the Minid Client. Currently, the Minid Client will collect some general info like "name" automatically from Globus Auth for use when registering new Minids. We probably want 'name' to be configurable based on the user's preference.

The previous Minid version saved the following information:

[general]
minid_server: http://minid.bd2k.org/minid
username: <Name>
email: <email>
orcid: <Orcid>
code: <code>

We may want to track minid_server but I don't think anything else applies. username and email were used to track user info for the old Minid Service. code was used to verify users. username, email, code is functionally replaced by Globus Auth. orcid currently isn't used, although we could add it if we wanted to supply it as additional metadata.

The MinidClient class should track configuration in a config variable, so it is accessible by both the SDK and the CLI.