Merge branch 'GSOC_text_detect_DNN_backend' of https://github.com/sghoshcvc/opencv_contrib into GSOC_text_detect_DNN_backend

merge conflict

* Replace OpenMP parallelization with OpenCV's general parallel_for_ to cover other backends than OpenMP.

* Fixed shadowing of range variable in C++11 mode.

Added USING_STD_NAMESPACE macro to text module

bioinspired: prevent call ocl implementation when log sampling is enabled in retina (there is no log sampling kernel)

fixes warning on MacOSX Xcode 8.3.3

* Added python bindings for whole rgbd module

* changed exposed constructors to static Ptr<class>::create() functions

* removed python bindings for isValidDepth*

* removed operator bindings