Add command permission checks

Level 0: Every user - Public commands
Level 1: Guild owners or members with respective admin role - Elevated guild commands
Level 2: Global admins - Every command including levels below

util/general.js

@@ -5,5 +5,11 @@ module.exports = {
     getBotProperty: async function(property) {
         let bot = await Bot.findOne();
         return property ? bot[property] : bot;
+    },
+
+    setBotProperty: async function(property, value) {
+        let bot = await Bot.findOne();
+        bot[property] = value;
+        await bot.save();
     }
 }