Update .gitignore datasets dir (#1577)

.gitignore

@@ -40,6 +40,11 @@ pycocotools/*
 results*.txt
 gcp_test*.sh
 
+# Datasets -------------------------------------------------------------------------------------------------------------
+coco/
+coco128/
+VOC/
+
 # MATLAB GitIgnore -----------------------------------------------------------------------------------------------------
 *.m~
 *.mat