jfjoch client: added function co call api to get diffraction image

daq/src/mxlibs3/jfjoch.py

@@ -153,3 +153,6 @@ class JFJochWrapper:
             raise Exception("no detectors configured")
 
         return l.detectors[l.current_id]
+
+    def get_diffraction_image(self, image_id: int):
+        return self.__api.image_buffer_image_jpeg_get(id=image_id, show_spots=False)