Granular permissions for bot usage (Mod, Admin etc.)

[Hector1801]

In Modmail, Moderators are users with the rights to use the bot and some of its functions, depending on the permissions we've gave them in the config.ini file. However, it would be cool if we could also set an Admin role, which basically, could have extra permissions like being able to edit & delete replies sent by other Moderators/Admins, something that is not possible at the moment.