Make Priority settable for on StaticEventBinders (#187)

The event engine has a concept of event binder priority, which it uses to determine what order the event binders should have when processing events.  This makes the Priority property settable for derived implementations of StaticEventBinder.

Protogame/Events/StaticEventBinder.cs

@@ -33,6 +33,7 @@ public abstract class StaticEventBinder<TContext> : IEventBinder<TContext>
         protected StaticEventBinder()
         {
             this._bindings = new List<Func<TContext, IEventEngine<TContext>, Event, bool>>();
+            Priority = 100;
         }
 
         protected interface IBindable<TEvent>
@@ -124,13 +125,7 @@ protected interface IBindableTo<TEvent, TTarget>
         {
         }
 
-        public int Priority
-        {
-            get
-            {
-                return 100;
-            }
-        }
+        public int Priority { get; set; }
 
         public void Assign(IKernel kernel)
         {