chore: upgrade to opencv 4

[guhur]

As described to the issue #80, we can easily upgrade the code to OpenCV 4.

OpenCV 4 is delivered by default in Ubuntu 20.04, and I updated the Dockerfile accordingly.

I observed I was often using the script linked in the issue and reproduced below. So why not creating a PR since it could ease the installation.

#!/bin/sh

find .  \( -name '*.cpp' -or -name '*.hpp' -or -name '*.h' \)  \
  -exec sed -i \
  -e 's/CV_IMWRITE_/cv::IMWRITE_/g' \
  -e 's/CV_LOAD_IMAGE_ANYDEPTH/cv::IMREAD_ANYDEPTH/g' \
  -e 's/CV_LOAD_IMAGE_COLOR/cv::IMREAD_COLOR/g' \
  -e 's/CV_L2/cv::NORM_L2/g' \
  -e 's/CV_TERMCRIT_EPS/cv::TermCriteria::EPS/g' \
  -e 's/CV_TERMCRIT_ITER/cv::TermCriteria::MAX_ITER/g' \
  -e 's/CV_CALIB_CB_/cv::CALIB_CB_/g' \
  -e 's/CV_BGR2GRAY/cv::COLOR_BGR2GRAY/g' \
  -e 's/CV_GRAY2BGR/cv::COLOR_GRAY2BGR/g' \
  -e 's/CV_HAAR_/cv::CASCADE_/g' \
  -e 's/CV_INTER_/cv::INTER_/g' \
  -e 's/CV_WARP_INVERSE_MAP/cv::WARP_INVERSE_MAP/g' \
  -e 's/CV_WINDOW_/cv::WINDOW_/g' \
  -e 's/CV_WND_/cv::WND_/g' \
  -e 's/CV_CAP_/cv::CAP_/g' \
  -e 's/CV_FOURCC/cv::VideoWriter::fourcc/g' \
  '{}' ';'

[ZhuFengdaaa]

cool, it works.

My issue on Ubuntu 20.04

/home/Matterport3DSimulator/src/lib/NavGraph.cpp: In member function ‘void mattersim::NavGraph::Location::loadCubemapImages()’:
/home/Matterport3DSimulator/src/lib/NavGraph.cpp:59:89: error: ‘CV_LOAD_IMAGE_ANYDEPTH’ was not declared in this scope
   59 |         cv::Mat depth = cv::imread(skyboxDir + viewpointId + "_skybox_depth_small.png", CV_LOAD_IMAGE_ANYDEPTH);
      |                                                                                         ^~~~~~~~~~~~~~~~~~~~~~
make[2]: *** [CMakeFiles/MatterSim.dir/build.make:90: CMakeFiles/MatterSim.dir/src/lib/NavGraph.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:106: CMakeFiles/MatterSim.dir/all] Error 2
make: *** [Makefile:91: all] Error 2