COCO Annotation IDs should begin with 1 (#748)

Currently the annotation ID begins with 0 which is interpreted by cocoapi as a false detection. The array dtm saves the matches via the ground truth annotation ID. The variable dtm is initialized as an array of zeros. 636becdc73/PythonAPI/pycocotools/cocoeval.py (L269)
636becdc73/PythonAPI/pycocotools/cocoeval.py (L295)
636becdc73/PythonAPI/pycocotools/cocoeval.py (L375)

cvat/apps/annotation/coco.py

@@ -264,7 +264,7 @@ def dump(file_object, annotations):
     insert_info_data(annotations, result_annotation)
     category_map = insert_categories_data(annotations, result_annotation)
 
-    segm_id = 0
+    segm_id = 1
     for img in annotations.group_by_frame():
         polygons = []