added keras-yolo3 conversion script and doc.

Added new extra script to support the conversion from keras-yolo3 project annotations. The extra/README.md has also been updated.

extra/README.md

@@ -18,10 +18,10 @@
     1) Add or update the class list to the file `class_list.txt`
     2) Use the parameter `--gt` to set the **ground-truth** source.
     3) Run the python script: `python3 convert_keras-yolo3.py --gt <gt_file_path>`
-    3.1) Supports only python 3.
-    3.2) This code can handle recursive annotation structure. Just use the `-r` parameter.
-    3.3) The converted annotation is placed by default in a new from_kerasyolo3 folder. You can change that with the parameter `-o`.
-    3.4) The format is defined according with github.com/qqwweee/keras-yolo3
+        1) Supports only python 3.
+        2) This code can handle recursive annotation structure. Just use the `-r` parameter.
+        3) The converted annotation is placed by default in a new from_kerasyolo3 folder. You can change that with the parameter `-o`.
+        4) The format is defined according with github.com/qqwweee/keras-yolo3
 
 ## Predicted:
 - ### convert darkflow `json` to our format:
@@ -41,10 +41,10 @@
     1) Add or update the class list to the file `class_list.txt`
     2) Use the parameter `--predicted` to set the **prediction** source.
     3) Run the python script: `python3 convert_keras-yolo3.py --pred <prediction_file_path>`
-    3.1) Supports only python 3.
-    3.2) This code can handle recursive annotation structure. Just use the `-r` parameter.
-    3.3) The converted annotation is placed by default in a new from_kerasyolo3 folder. You can change that with the parameter `-o`.
-    3.4) The format is defined according with github.com/gustavovaliati/keras-yolo3
+        1) Supports only python 3.
+        2) This code can handle recursive annotation structure. Just use the `-r` parameter.
+        3) The converted annotation is placed by default in a new from_kerasyolo3 folder. You can change that with the parameter `-o`.
+        4) The format is defined according with github.com/gustavovaliati/keras-yolo3
 
 ## Remove specific char delimiter from files