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

Revert "documentation: avoid links to 'master' branch from 3.4 maintenance branch"
This reverts commit 9ba9358ecb.

Revert "documentation: avoid links to 'master' branch from 3.4 maintenance branch (2)"
This reverts commit f185802489.

doc/tutorials/features2d/trackingmotion/good_features_to_track/good_features_to_track.markdown

@@ -6,7 +6,7 @@ Goal
 
 In this tutorial you will learn how to:
 
--   Use the function @ref cv::goodFeaturesToTrack to detect corners using the Shi-Tomasi method.
+-   Use the function @ref cv::goodFeaturesToTrack to detect corners using the Shi-Tomasi method (@cite Shi94).
 
 Theory
 ------
@@ -14,9 +14,23 @@ Theory
 Code
 ----
 
+@add_toggle_cpp
 This tutorial code's is shown lines below. You can also download it from
 [here](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/TrackingMotion/goodFeaturesToTrack_Demo.cpp)
 @include samples/cpp/tutorial_code/TrackingMotion/goodFeaturesToTrack_Demo.cpp
+@end_toggle
+
+@add_toggle_java
+This tutorial code's is shown lines below. You can also download it from
+[here](https://github.com/opencv/opencv/tree/master/samples/java/tutorial_code/TrackingMotion/good_features_to_track/GoodFeaturesToTrackDemo.java)
+@include samples/java/tutorial_code/TrackingMotion/good_features_to_track/GoodFeaturesToTrackDemo.java
+@end_toggle
+
+@add_toggle_python
+This tutorial code's is shown lines below. You can also download it from
+[here](https://github.com/opencv/opencv/tree/master/samples/python/tutorial_code/TrackingMotion/good_features_to_track/goodFeaturesToTrack_Demo.py)
+@include samples/python/tutorial_code/TrackingMotion/good_features_to_track/goodFeaturesToTrack_Demo.py
+@end_toggle
 
 Explanation
 -----------
@@ -24,4 +38,4 @@ Explanation
 Result
 ------
 
-![](images/Feature_Detection_Result_a.jpg)
+![](images/good_features_to_track_Shi_Tomasi.jpg)