Early behavior fixups:

- Priorities are now higher number -> higher priority
- Priorities are now actually respected
- Early behaviors now print custom messages when they perform an action (Filter trigger, blacklist, poll vote, etc)
- small cleanup

src/NadekoBot/Common/ModuleBehaviors/IEarlyBehavior.cs

@@ -0,0 +1,14 @@
+using System.Threading.Tasks;
+using Discord;
+
+namespace NadekoBot.Common.ModuleBehaviors
+{
+    /// <summary>
+    /// Implemented by modules which block execution before anything is executed
+    /// </summary>
+    public interface IEarlyBehavior
+    {
+        int Priority { get; }
+        Task<bool> RunBehavior(IGuild guild, IUserMessage msg);
+    }
+}