Merge 2.4 into master

Original pull requests:

* #2107 from nghiaho12:nn_doc
* #2171 from djetter99:fix_static_init_order
* #2175 from vrabaud:2.4
* #2181 from asmorkalov:ocv_packaging
* #2183 from jet47:cuda-hough-fix (skipped per discussion with @jet47)
* #2188 from jet47:gpumat-copyto-fix
* #2193 from apavlenko:2.4_lic_remove
* #2194 from apavlenko:2.4_perf_haar_iter
* #2197 from asmorkalov:ocv_packaging2