Merge remote-tracking branch 'upstream/3.4' into merge-3.4

doc/tutorials/dnn/dnn_android/dnn_android.markdown

@@ -1,5 +1,8 @@
 # How to run deep networks on Android device {#tutorial_dnn_android}
 
+@prev_tutorial{tutorial_dnn_halide_scheduling}
+@next_tutorial{tutorial_dnn_yolo}
+
 ## Introduction
 In this tutorial you'll know how to run deep learning networks on Android device
 using OpenCV deep learning module.

doc/tutorials/dnn/dnn_custom_layers/dnn_custom_layers.md

@@ -1,5 +1,7 @@
 # Custom deep learning layers support {#tutorial_dnn_custom_layers}
 
+@prev_tutorial{tutorial_dnn_javascript}
+
 ## Introduction
 Deep learning is a fast growing area. The new approaches to build neural networks
 usually introduce new types of layers. They could be modifications of existing

doc/tutorials/dnn/dnn_googlenet/dnn_googlenet.markdown

@@ -1,6 +1,8 @@
 Load Caffe framework models  {#tutorial_dnn_googlenet}
 ===========================
 
+@next_tutorial{tutorial_dnn_halide}
+
 Introduction
 ------------
 

doc/tutorials/dnn/dnn_halide/dnn_halide.markdown

@@ -1,5 +1,8 @@
 # How to enable Halide backend for improve efficiency  {#tutorial_dnn_halide}
 
+@prev_tutorial{tutorial_dnn_googlenet}
+@next_tutorial{tutorial_dnn_halide_scheduling}
+
 ## Introduction
 This tutorial guidelines how to run your models in OpenCV deep learning module
 using Halide language backend. Halide is an open-source project that let us

doc/tutorials/dnn/dnn_halide_scheduling/dnn_halide_scheduling.markdown

@@ -1,5 +1,8 @@
 # How to schedule your network for Halide backend {#tutorial_dnn_halide_scheduling}
 
+@prev_tutorial{tutorial_dnn_halide}
+@next_tutorial{tutorial_dnn_android}
+
 ## Introduction
 Halide code is the same for every device we use. But for achieving the satisfied
 efficiency we should schedule computations properly. In this tutorial we describe

doc/tutorials/dnn/dnn_javascript/dnn_javascript.markdown

@@ -1,5 +1,8 @@
 # How to run deep networks in browser {#tutorial_dnn_javascript}
 
+@prev_tutorial{tutorial_dnn_yolo}
+@next_tutorial{tutorial_dnn_custom_layers}
+
 ## Introduction
 This tutorial will show us how to run deep learning models using OpenCV.js right
 in a browser. Tutorial refers a sample of face detection and face recognition

doc/tutorials/dnn/dnn_yolo/dnn_yolo.markdown

@@ -1,6 +1,9 @@
 YOLO DNNs  {#tutorial_dnn_yolo}
 ===============================
 
+@prev_tutorial{tutorial_dnn_android}
+@next_tutorial{tutorial_dnn_javascript}
+
 Introduction
 ------------