add support for yolo dataset

data/metadata.yml

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+!!python/object:pita_dataset.yolo_annotations.YOLOConfig
+names:
+  0: logo
+  1: text
+nc: 2
+path: data
+test: test-yolo/images
+train: train-yolo/images
+val: val-yolo/images

data/test-yolo.zip

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:30665c59b81904aa0b767fdc513b40f536fbdd9ab10a7bfa62368f31d827430e
+size 1184434

data/train-yolo.zip

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:557ede61b28b0fd15cf390ed6701848725dc8b9f4318416558a6405298ccf462
+size 4199344

data/val-yolo.zip

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:3b36ac1555b35cce5f9a6aaac344a2976b98f7d1103bf4dc13264fb42b2e2008
+size 771760