Support permissions file

Created by: agraubert

Check for a permissions.yml file

Allow permissions by User+discriminator, user id, role name, role id. (Non-id formats should be modified by bot on startup to use the id since names can change, and this would only assume that names are correct when permission is first added)

Permissions can allow or deny specific commands as well as underscore commands as a whole. effective permission for a command is user-specific then highest (in yml) role that has a permission defined.

Default permissions for @everyone roll is to automatically deny all underscore commands and allow all others.

Add a permissions command to modify permissions without restart