Initial/reset progress.json for new training run

progress.json

@@ -0,0 +1,9 @@
+{
+  "sessions_completed": 0,
+  "total_steps_completed": 0,
+  "latest_checkpoint": null,
+  "shard_size_examples": 500,
+  "total_examples": 506,
+  "next_start_index": 0,
+  "history": []
+}