changed data/loaders and engine/predictor so they accept 1 channel images for predictions

ultralytics/data/loaders.py

@@ -249,7 +249,7 @@ class LoadImages:
         else:
             # Read image
             self.count += 1
-            im0 = cv2.imread(path)  # BGR
+            im0 = cv2.imread(path, cv2.IMREAD_GRAYSCALE)  # BGR
             if im0 is None:
                 raise FileNotFoundError(f'Image Not Found {path}')
             s = f'image {self.count}/{self.nf} {path}: '