Set channel type to RGB(A) for 3 & 4 channel images in natvis Image v…

…isualiser

This sets the channel type to RGB and RGBA for 3 and 4-channel images respectively, for the eos::core::Image natvis (Image Watch) visualiser.
With this improvement, Image Watch displays our RGB(A) eos::core::Images with correct colours, and doesn't interpret them as BGR (its default) anymore.

.natvis/eos.natvis

@@ -54,7 +54,13 @@
         <DisplayString>FLOAT64</DisplayString>
       </Synthetic>
 
-      <Item Name="[channels]">$T2</Item>
+      <Synthetic Name="[channels]" Condition='$T2 == 3'>
+        <DisplayString>RGB</DisplayString>
+      </Synthetic>
+      <Synthetic Name="[channels]" Condition='$T2 == 4'>
+        <DisplayString>RGBA</DisplayString>
+      </Synthetic>
+      <!-- Note: I haven't found out how to do "if $T2 is not 3 or 4, then just use $T2". -->
 
       <Item Name="[width]">width_</Item>
       <Item Name="[height]">height_</Item>