build: transition to C++17, minor changes in documentation

samples/install/linux_quick_install.sh

@@ -9,7 +9,7 @@ fi
 
 # [body]
 # Install minimal prerequisites (Ubuntu 18.04 as reference)
-sudo apt update && sudo apt install -y cmake g++ wget unzip
+sudo apt update && sudo apt install -y cmake g++ wget unzip ninja-build
 
 # Download and unpack sources
 wget -O opencv.zip https://github.com/opencv/opencv/archive/5.x.zip
@@ -19,7 +19,7 @@ unzip opencv.zip
 mkdir -p build && cd build
 
 # Configure
-cmake  ../opencv-5.x
+cmake -GNinja  ../opencv-5.x
 
 # Build
 cmake --build .