Sanitize ImageDimensions base class

- Make `width` and `height` private
- Drop `getW()` and `getH()`
- Clean `PreviewProps`

rtengine/dcrop.cc

@@ -113,7 +113,7 @@ void Crop::setEditSubscriber(EditSubscriber* newSubscriber)
             PipetteBuffer::LabBuffer = nullptr;
         }
 
-        if (PipetteBuffer::singlePlaneBuffer.getW() != -1) {
+        if (PipetteBuffer::singlePlaneBuffer.getWidth() != -1) {
             PipetteBuffer::singlePlaneBuffer.flushData();
         }
     }