doc: tutorial refactor

doc/tutorials/tutorials.markdown

@@ -4,18 +4,12 @@ OpenCV Tutorials {#tutorial_root}
 - @subpage tutorial_table_of_content_introduction - build and install OpenCV on your computer
 - @subpage tutorial_table_of_content_core - basic building blocks of the library
 - @subpage tutorial_table_of_content_imgproc - image processing functions
-- @subpage tutorial_table_of_content_highgui - built-in graphical user interface
-- @subpage tutorial_table_of_content_imgcodecs - read and write images from/to files using _imgcodecs_ module
-- @subpage tutorial_table_of_content_videoio - read and write videos using _videio_ module
+- @subpage tutorial_table_of_content_app - application utils (GUI, image/video input/output)
 - @subpage tutorial_table_of_content_calib3d - extract 3D world information from 2D images
 - @subpage tutorial_table_of_content_features2d - feature detectors, descriptors and matching framework
-- @subpage tutorial_table_of_content_video - algorithms for video streams: motion detection, object and feature tracking, etc.
-- @subpage tutorial_table_of_content_objdetect - detect objects using conventional CV methods
 - @subpage tutorial_table_of_content_dnn - infer neural networks using built-in _dnn_ module
-- @subpage tutorial_table_of_content_ml - machine learning algorithms for statistical classification, regression and data clustering
 - @subpage tutorial_table_of_content_gapi - graph-based approach to computer vision algorithms building
-- @subpage tutorial_table_of_content_photo - advanced photo processing
-- @subpage tutorial_table_of_content_stitching - create panoramas and more using _stitching_ module
+- @subpage tutorial_table_of_content_other - other modules (ml, objdetect, stitching, video, photo)
 - @subpage tutorial_table_of_content_ios - running OpenCV on an iDevice
 @cond CUDA_MODULES
 - @subpage tutorial_table_of_content_gpu - utilizing power of video card to run CV algorithms