Merge remote-tracking branch 'origin/master' into 1.9

# Conflicts:
#	Source/Editor/Modules/ContentDatabaseModule.cs
#	Source/Editor/Surface/SurfaceUtils.cs
#	Source/Editor/Windows/Assets/MaterialInstanceWindow.cs
#	Source/Engine/Foliage/Foliage.cpp
#	Source/Engine/Graphics/Models/MeshBase.h
#	Source/Engine/Tools/MaterialGenerator/MaterialGenerator.Textures.cpp

Source/Engine/Graphics/PostProcessSettings.h

@@ -52,6 +52,11 @@ API_ENUM() enum class ToneMappingMode
     /// The ACES Filmic reference tonemapper (approximation).
     /// </summary>
     ACES = 2,
+
+    /// <summary>
+    /// The AGX tonemapper.
+    /// </summary>
+    AGX = 3,
 };
 
 /// <summary>