Deletes the specified custom user settings for a single user.
###Deleting Grouped Custom User Settings###
If the custom user settings you want to delete are grouped, you must include the following information in the header, after Content-Type, in the request:
group_name is your designated name for the group of customer user settings.
If the extra header information is not included, only the custom user settings that were added without a group are deleted.
The external account number (int) or account ID GUID.
The ID of the user to access. Generally this is the ID of the current authenticated user, but if the authenticated user is an Administrator on the account,