Tagging interface for event handlers

Support events in the TorchAPI
Static registry, non-static registration methods.
Support unregister by assembly.

Torch.API/Managers/Event/EventHandlerAttribute.cs

@@ -0,0 +1,28 @@
+using System;
+
+namespace Torch.API.Managers.Event
+{
+    /// <summary>
+    /// Attribute indicating that a method should be invoked when the event occurs.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method)]
+    public class EventHandlerAttribute : Attribute
+    {
+        /// <summary>
+        /// Events are executed from low priority to high priority.
+        /// </summary>
+        /// <remarks>
+        /// While this may seem unintuitive this gives the high priority events the final say on changing/canceling events.
+        /// </remarks>
+        public int Priority { get; set; } = 0;
+
+        /// <summary>
+        /// Specifies if this handler should ignore a consumed event.
+        /// </summary>
+        /// <remarks>
+        /// If <see cref="SkipCancelled"/> is <em>true</em> and the event is cancelled by a lower priority handler this handler won't be invoked.
+        /// </remarks>
+        /// <seealso cref="IEvent.Cancelled"/>
+        public bool SkipCancelled { get; set; } = false;
+    }
+}

Torch.API/Managers/Event/IEvent.cs

@@ -0,0 +1,11 @@
+namespace Torch.API.Managers.Event
+{
+    public interface IEvent
+    {
+        /// <summary>
+        /// An event that has been cancelled will no be processed in the default manner.
+        /// </summary>
+        /// <seealso cref="EventHandlerAttribute.SkipCancelled"/>
+        bool Cancelled { get; }
+    }
+}

Torch.API/Managers/Event/IEventHandler.cs

@@ -0,0 +1,9 @@
+namespace Torch.API.Managers.Event
+{
+    /// <summary>
+    /// Interface used to tag an event handler.  This does <b>not</b> register it with the event manager.
+    /// </summary>
+    public interface IEventHandler
+    {
+    }
+}

Torch.API/Managers/Event/IEventManager.cs

@@ -0,0 +1,27 @@
+using System.Runtime.CompilerServices;
+
+namespace Torch.API.Managers.Event
+{
+    /// <summary>
+    /// Manager class responsible for registration of event handlers.
+    /// </summary>
+    public interface IEventManager
+    {
+        /// <summary>
+        /// Registers all event handler methods contained in the given instance 
+        /// </summary>
+        /// <param name="handler">Instance to register</param>
+        /// <returns><b>true</b> if added, <b>false</b> otherwise</returns>
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        bool RegisterHandler(IEventHandler handler);
+
+
+        /// <summary>
+        /// Unregisters all event handler methods contained in the given instance 
+        /// </summary>
+        /// <param name="handler">Instance to unregister</param>
+        /// <returns><b>true</b> if removed, <b>false</b> otherwise</returns>
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        bool UnregisterHandler(IEventHandler handler);
+    }
+}