Add ExclusiveGroups comments

DispatchOnChange and DispatchOnSet must receive an EGID (sorry)
Rename GenericEntityDescriptorHolder to UnityEntityDescriptorHolder

Svelto.ECS/Dispatcher/DispatchOnChange.cs

@@ -6,6 +6,9 @@ namespace Svelto.ECS
     {
         public DispatchOnChange(int senderID) : base(senderID)
         { }
+        
+        public DispatchOnChange(EGID senderID) : base(senderID)
+        { }
 
         public DispatchOnChange() {}
 

Svelto.ECS/Dispatcher/DispatchOnSet.cs

@@ -4,16 +4,20 @@ namespace Svelto.ECS
 {
     public class DispatchOnSet<T> where T:struct
     {
-        public DispatchOnSet(int senderID)
+        public DispatchOnSet(int senderID):this()
+        {
+            _senderID    = new EGID(senderID, ExclusiveGroup.StandardEntitiesGroup);
+        }
+        
+        public DispatchOnSet(EGID senderID):this()
         {
             _senderID = senderID;
-            _subscribers = new WeakEvent<int, T>();
         }
         
         public DispatchOnSet()
         {
-            _senderID    = -1;
-            _subscribers = new WeakEvent<int, T>();
+            _senderID    = new EGID();
+            _subscribers = new WeakEvent<EGID, T>();
         }
 
         public T value
@@ -30,20 +34,20 @@ namespace Svelto.ECS
                 return _value;
             }
         }
-
-        public void NotifyOnValueSet(System.Action<int, T> action)
+        
+        public void NotifyOnValueSet(System.Action<EGID, T> action)
         {
             _subscribers += action;
         }
 
-        public void StopNotify(System.Action<int, T> action)
+        public void StopNotify(System.Action<EGID, T> action)
         {
             _subscribers -= action;
         }
 
         protected T      _value;
-        readonly int    _senderID;
+        readonly EGID _senderID;
 
-        WeakEvent<int, T> _subscribers;
+        WeakEvent<EGID, T> _subscribers;
     }
 }

Svelto.ECS/EGID.cs

@@ -33,7 +33,12 @@ namespace Svelto.ECS
 
         static long MAKE_GLOBAL_ID(int entityId, int groupId)
         {
-            return (long)groupId << 32 | (((long)(uint)entityId) & 0xFFFFFFFF);
+            return (long)groupId << 32 | ((long)(uint)entityId & 0xFFFFFFFF);
+        }
+        
+        public static implicit operator int(EGID id) 
+        {
+            return id.entityID;
         }
     }
 }

Svelto.ECS/ExclusiveGroups.cs

@@ -1,5 +1,16 @@
 namespace Svelto.ECS
 {
+    /// <summary>
+    /// Exclusive Groups guarantee that the GroupID is unique.
+    ///
+    /// The best way to use it is like:
+    ///
+    /// public static class MyExclusiveGroups //(can be as many as you want)
+    /// {
+    ///     public static MyExclusiveGroup1 = new ExclusiveGroup();
+    /// }
+    /// </summary>
+    
     public class ExclusiveGroup
     {
         internal const int StandardEntitiesGroup = int.MaxValue;
@@ -10,6 +21,9 @@
             _globalId += 1;
         }
 
+        /// <summary>
+        /// Use this constructor to reserve N groups
+        /// </summary>
         public ExclusiveGroup(int range)
         {
             _id       =  _globalId;

Svelto.ECS/Extensions/Unity/UnityEntityDescriptorHolder.cs

@@ -0,0 +1,14 @@
+#if UNITY_5 || UNITY_5_3_OR_NEWER
+namespace Svelto.ECS
+{
+    public class UnityEntityDescriptorHolder<T>: 
+        UnityEngine.MonoBehaviour , IEntityDescriptorHolder
+            where T: IEntityDescriptor, new()
+    {
+        public IEntityBuilder[] GetEntitiesToBuild()
+        {
+            return EntityDescriptorTemplate<T>.descriptor.entitiesToBuild;
+        }
+    }
+}
+#endif