Create Graphics library. (#316)

* Fix BoundingRect unit tests.

* Create `graphics` library.

Source/MonoGame.Extended.Graphics/Batching/IBatchDrawCommandData.cs

@@ -0,0 +1,25 @@
+using System;
+using Microsoft.Xna.Framework.Graphics;
+
+namespace MonoGame.Extended.Graphics.Batching
+{
+    /// <summary>
+    ///     Defines the data for batch draw commands.
+    /// </summary>
+    /// <typeparam name="TCommandData">The type of the batch draw command data.</typeparam>
+    /// <seealso cref="Extended.IEquatableByRef{TBatchDrawCommandData}" />
+    public interface IBatchDrawCommandData<TCommandData> : IEquatableByRef<TCommandData>, IComparable<TCommandData>
+    {
+        /// <summary>
+        ///     Applies the parameters for the <see cref="IBatchDrawCommandData{TBatchDrawCommandData}" /> to the specified
+        ///     <see cref="Effect" />.
+        /// </summary>
+        /// <param name="effect">The effect.</param>
+        void ApplyTo(Effect effect);
+
+        /// <summary>
+        ///     Sets all the associated references to <code>null</code>.
+        /// </summary>
+        void SetReferencesToNull();
+    }
+}