add manuscript for exporting lite model

deploy/lite/export_lite.py

+import paddlelite.lite as lite
+import os
+import argparse
+
+
+def export_lite():
+    opt = lite.Opt()
+    model_file = os.path.join(FLAGS.model_path, '__model__')
+    params_file = os.path.join(FLAGS.model_path, '__params__')
+    opt.run_optimize("", model_file, params_file, FLAGS.place, FLAGS.save_dir)
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "--model_path",
+        type=str,
+        default="",
+        help="model path.",
+        required=True)
+    parser.add_argument(
+        "--place",
+        type=str,
+        default="arm",
+        help="preprocess config path.",
+        required=True)
+    parser.add_argument(
+        "--save_dir",
+        type=str,
+        default="paddlex.onnx",
+        help="Directory for storing the output visualization files.",
+        required=True)
+    FLAGS = parser.parse_args()
+    export_lite()