Remove ToLayer_ID calls from color checks

Colors are assigned to virtual layers while the ToLayer_ID returns a
physical layer enum.  The GetLayerColor/SetLayerColor take LAYER_NUM
(int) values that can be larger than the physical layer count.

pcbnew/pcb_layer_box_selector.cpp

@@ -150,7 +150,7 @@ COLOR4D PCB_LAYER_BOX_SELECTOR::GetLayerColor( LAYER_NUM aLayer ) const
 {
     wxASSERT( m_boardFrame );
 
-    return m_boardFrame->Settings().Colors().GetLayerColor( ToLAYER_ID( aLayer ) );
+    return m_boardFrame->Settings().Colors().GetLayerColor( aLayer );
 }
 
 

pcbnew/pcb_layer_widget.cpp

@@ -584,11 +584,11 @@ void PCB_LAYER_WIDGET::OnLayerColorChange( int aLayer, COLOR4D aColor )
     // destroys the GAL color setup
     if( !myframe->IsGalCanvasActive() )
     {
-        COLOR4D oldColor = myframe->Settings().Colors().GetLayerColor( ToLAYER_ID( aLayer ) );
+        COLOR4D oldColor = myframe->Settings().Colors().GetLayerColor( aLayer );
         aColor.a = oldColor.a;
     }
 
-    myframe->Settings().Colors().SetLayerColor( ToLAYER_ID( aLayer ), aColor );
+    myframe->Settings().Colors().SetLayerColor( aLayer, aColor );
 
     if( myframe->IsGalCanvasActive() )
     {

pcbnew/plot_brditems_plotter.cpp

@@ -56,7 +56,7 @@
 
 COLOR4D BRDITEMS_PLOTTER::getColor( LAYER_NUM aLayer )
 {
-    COLOR4D color = m_board->Colors().GetLayerColor( ToLAYER_ID( aLayer ) );
+    COLOR4D color = m_board->Colors().GetLayerColor( aLayer );
 
     // A hack to avoid plotting ahite itmen in white color, expecting the paper
     // is also white: use a non white color:

pcbnew/sel_layer.cpp

@@ -61,7 +61,7 @@ protected:
     // Virtual function
     COLOR4D GetLayerColor( LAYER_NUM aLayer ) const override
     {
-        return m_frame->Settings().Colors().GetLayerColor( ToLAYER_ID( aLayer ) );
+        return m_frame->Settings().Colors().GetLayerColor( aLayer );
     }
 
     // Returns the name of the layer id