Added policies. Added action for channel ad break ending.

Chat/Commands/Limits/IUsagePolicy.cs

@@ -0,0 +1,10 @@
+namespace TwitchChatTTS.Chat.Commands.Limits
+{
+    public interface IUsagePolicy<K>
+    {
+        void Remove(string group, string policy);
+        void Set(string group, string policy, int count, TimeSpan span);
+        bool TryUse(K key, string group, string policy);
+        public bool TryUse(K key, IEnumerable<string> groups, string policy);
+    }
+}