Allow admins to configure what should be in a short nightscout reply

[cascer1]

currently the contents of a short nightscout reply are hard-coded to only exclude the users profile picture. Instead, there should be a command that allows admins to configure which fields should be allowed.

When posting a reply, also consider what fields a user has configured. Only show fields that are allowed by the short config and that the user has configured.

For example: Short config allows bg, iob, and trend. User has configured bg, cob, and trend. Reply should only contain bg and trend.