Brushes - Added brush presets

ColorGradient - Refactored so it implements IList

src/Artemis.Core/Models/Profile/LayerProperties/ILayerProperty.cs

@@ -33,6 +33,11 @@ namespace Artemis.Core
         /// </summary>
         Type PropertyType { get; }
 
+        /// <summary>
+        ///     Indicates whether the BaseValue was loaded from storage, useful to check whether a default value must be applied
+        /// </summary>
+        bool IsLoadedFromStorage { get; }
+
         /// <summary>
         ///     Initializes the layer property
         ///     <para>