Migrate batch norm layer

include/tensor.hpp

@@ -45,6 +45,11 @@ public:
 
     void zero();
 
+    template <typename T>
+    void fill(T value) {
+        backend->fill(*this, value);
+    }
+
     template <typename T>
     void set_data(T *data) {
         backend->copy_to_device(*this, data, total_size);