Converts the ad-hoc design of the Material Editor to utilize the same inspector interface as most everything else does.

- Overhauls the material editor to simplify and streamline the logic behind it since the inspector does most of the work
- Tweak a few order positions of materialdefinition fields to work better
- Sets AO, Rough and Metal channel fields to use an enum type for human readability
- Updates the MaterialPreview gui control to work with assetIds
- MatEd now supports setting of parent material to inherit from
- Creating a new material now can prompt selecting an existing material to inherit from
- Can now edit the mapTo value of a material in the matEd
- New standalone Composite Texture Editor window for convering AO, Roughness and Metalness maps in a material to an ORMMap
- Can also star the creation of a composite texture via RMB context menu in AB on an image asset
- Moved logic of CubemapEditor from MatEd to it's own stuff
- Made ImageAsset fields now be more clear when they have nothing assigned, and also have a clear button to empty the field's value so it's consistent across the board
- Reorganized the layout of the gui and image files for the MatEd to be easier to navigate
- MaterialEditor now overlays the EditorGUI instead of being forcefully embedded in it, allowing easy editing of the MatEd Gui via the Gui editor

Engine/source/materials/materialDefinition.h

@@ -129,6 +129,14 @@ public:
       Square,
    };
 
+   enum SourceChannelType
+   {
+      RedChannel = 0,
+      GreenChannel,
+      BlueChannel,
+      AlphaChannel
+   };
+
    class StageData
    {
    protected:
@@ -425,9 +433,11 @@ private:
 typedef Material::AnimType MaterialAnimType;
 typedef Material::BlendOp MaterialBlendOp;
 typedef Material::WaveType MaterialWaveType;
+typedef Material::SourceChannelType MaterialSourceChannelType;
 
 DefineBitfieldType(MaterialAnimType);
 DefineEnumType(MaterialBlendOp);
 DefineEnumType(MaterialWaveType);
+DefineEnumType(MaterialSourceChannelType);
 
 #endif // _MATERIALDEFINITION_H_