Moved brush calculation mode to the brush

This makes obviously more sense ...

Brushes/AbstractBrush.cs

@@ -1,6 +1,7 @@
 // ReSharper disable VirtualMemberNeverOverriden.Global
 
 using System.Drawing;
+using CUE.NET.Devices.Keyboard.Enums;
 using CUE.NET.Helper;
 
 namespace CUE.NET.Brushes
@@ -12,6 +13,11 @@ namespace CUE.NET.Brushes
     {
         #region Properties & Fields
 
+        /// <summary>
+        /// Gets or sets the calculation mode used for the rectangle/points used for color-selection in brushes.
+        /// </summary>
+        public BrushCalculationMode BrushCalculationMode { get; set; } = BrushCalculationMode.Relative;
+
         /// <summary>
         /// Gets or sets the overall percentage brightness of the brush.
         /// </summary>

Brushes/IBrush.cs

@@ -1,6 +1,7 @@
 // ReSharper disable UnusedMemberInSuper.Global
 
 using System.Drawing;
+using CUE.NET.Devices.Keyboard.Enums;
 
 namespace CUE.NET.Brushes
 {
@@ -9,6 +10,11 @@ namespace CUE.NET.Brushes
     /// </summary>
     public interface IBrush
     {
+        /// <summary>
+        /// Gets or sets the calculation mode used for the rectangle/points used for color-selection in brushes.
+        /// </summary>
+        BrushCalculationMode BrushCalculationMode { get; set; }
+
         /// <summary>
         /// Gets or sets the overall percentage brightness of the brush.
         /// </summary>