Made API models internal. Removed Discord.Net.API.

src/Discord.Net.Rest/API/EntityOrId.cs

@@ -0,0 +1,19 @@
+namespace Discord.API
+{
+    internal struct EntityOrId<T>
+    {
+        public ulong Id { get; }
+        public T Object { get; }
+
+        public EntityOrId(ulong id)
+        {
+            Id = id;
+            Object = default(T);
+        }
+        public EntityOrId(T obj)
+        {
+            Id = 0;
+            Object = obj;
+        }
+    }
+}