add checkpoints and config system

convert from bbox oriented and pascal xml
fixes

config.py

@@ -0,0 +1,22 @@
+import yaml
+
+config_file = 'config.yaml'
+
+
+class Config:
+
+    def __init__(self):
+        with open(config_file, 'r') as f:
+            c = yaml.safe_load(f)
+            self.checkpoint = c['checkpoint']
+            self.images_dir = c['images_dir']
+            self.labels_dir = c['labels_dir']
+            f.close()
+
+    def write(self):
+        with open(config_file, 'w') as f:
+            d = dict(checkpoint=self.checkpoint,
+                     images_dir=self.images_dir,
+                     labels_dir=self.labels_dir)
+            yaml.safe_dump(d, f)
+            f.close()