Synchronized reading from camera with heavy frame processing
provides bad effects (huge frame latency, processing frames from the past).
Generally, there is no way to process each frame and some frames will be dropped.
Allow preventive frame dropping to reduce lag of processed frames.

This mode is applied to cameras only (opened by 'index').

Use Win32 TRUE/FALSE in SetUINT32() calls for bool parameters

to control DNN_BACKEND_DEFAULT enumeration value behavior

`camid` value is always -1 after close().

* setTo_#10507

* setTo_Nan_10507

* setTo: update check / test for NaNs

Add Java and Python code for the following imgproc tutorials: Finding contours in your image, Convex Hull, Creating Bounding boxes and circles for contours, Creating Bounding rotated boxes and ellipses for contours, Image Moments, Point Polygon Test.

Improve experience of launching app from explorer:
- application just flash (open/close) the console window
Suggested Win32 application flavor additionally shows MessageBox
and waits for User interaction.

64-bit only

- build "opencv_version" only: `cmake -DBUILD_APPS_LIST=version ...`
- option 'BUILD_opencv_apps' should be 'ON'

- no behavior changes in grabFrame()
- added Lock2D() support into retrieveFrame()