Import SSDs from TensorFlow by training config (#12188)

* Remove TensorFlow and protobuf dependencies from object detection scripts

* Create text graphs for TensorFlow object detection networks from sample

modules/dnn/include/opencv2/dnn/dnn.hpp

@@ -885,6 +885,14 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
     CV_EXPORTS_W void shrinkCaffeModel(const String& src, const String& dst,
                                        const std::vector<String>& layersTypes = std::vector<String>());
 
+    /** @brief Create a text representation for a binary network stored in protocol buffer format.
+     *  @param[in] model  A path to binary network.
+     *  @param[in] output A path to output text file to be created.
+     *
+     *  @note To reduce output file size, trained weights are not included.
+     */
+    CV_EXPORTS_W void writeTextGraph(const String& model, const String& output);
+
     /** @brief Performs non maximum suppression given boxes and corresponding scores.
 
      * @param bboxes a set of bounding boxes to apply NMS.