add DataChunkFlat constructors with the vector initialization

Author: robertsulej

keras_model.h

@@ -77,7 +77,12 @@ class keras::DataChunk2D : public keras::DataChunk {
 
 class keras::DataChunkFlat : public keras::DataChunk {
 public:
+  DataChunkFlat(size_t size) : f(size) { }
+  DataChunkFlat(size_t size, float init) : f(size, init) { }
+  DataChunkFlat(void) { }
+
   std::vector<float> f;
+  std::vector<float> & get_1d_rw() { return f; }
   std::vector<float> const & get_1d() const { return f; }
   void set_data(std::vector<float> const & d) { f = d; };
   size_t get_data_dim(void) const { return 1; }