about BYPRODUCTS bin/opencv-340.jar

Documentation generation refactoring (#10621)

* Documentation build updates:

- disable documentation by default, do not add to ALL target
- combine Doxygen and Javadoc
- optimize Doxygen html

* javadoc: fix path in build directory

* cmake: fix "Documentation" status line

intermediate commit (to simplify code review)

Based on pull request #31 (thanks to Eric Christiansen)
Support for Java is turned off by default and can be enabled setting
BUILD_opencv_java to ON (e.g. cmake -DBUILD_opencv_java=ON ..)