feat: 切换后端至PaddleOCR-NCNN，切换工程为CMake

1.项目后端整体迁移至PaddleOCR-NCNN算法，已通过基本的兼容性测试
2.工程改为使用CMake组织，后续为了更好地兼容第三方库，不再提供QMake工程
3.重整权利声明文件，重整代码工程，确保最小化侵权风险

Log: 切换后端至PaddleOCR-NCNN，切换工程为CMake
Change-Id: I4d5d2c5d37505a4a24b389b1a4c5d12f17bfa38c

3rdparty/opencv-4.5.4/modules/videoio/cmake/detect_ffmpeg.cmake

@@ -0,0 +1,129 @@
+# --- FFMPEG ---
+if(NOT HAVE_FFMPEG AND OPENCV_FFMPEG_USE_FIND_PACKAGE)
+  if(OPENCV_FFMPEG_USE_FIND_PACKAGE STREQUAL "1" OR OPENCV_FFMPEG_USE_FIND_PACKAGE STREQUAL "ON")
+    set(OPENCV_FFMPEG_USE_FIND_PACKAGE "FFMPEG")
+  endif()
+  find_package(${OPENCV_FFMPEG_USE_FIND_PACKAGE}) # Required components: AVCODEC AVFORMAT AVUTIL SWSCALE
+  if(FFMPEG_FOUND OR FFmpeg_FOUND)
+    set(HAVE_FFMPEG TRUE)
+  endif()
+endif()
+
+if(NOT HAVE_FFMPEG AND WIN32 AND NOT ARM AND NOT OPENCV_FFMPEG_SKIP_DOWNLOAD)
+  include("${OpenCV_SOURCE_DIR}/3rdparty/ffmpeg/ffmpeg.cmake")
+  download_win_ffmpeg(FFMPEG_CMAKE_SCRIPT)
+  if(FFMPEG_CMAKE_SCRIPT)
+    include("${FFMPEG_CMAKE_SCRIPT}")
+    set(HAVE_FFMPEG TRUE)
+    set(HAVE_FFMPEG_WRAPPER TRUE)
+  endif()
+endif()
+
+set(_required_ffmpeg_libraries libavcodec libavformat libavutil libswscale)
+set(_used_ffmpeg_libraries ${_required_ffmpeg_libraries})
+if(NOT HAVE_FFMPEG AND PKG_CONFIG_FOUND)
+  ocv_check_modules(FFMPEG libavcodec libavformat libavutil libswscale)
+  if(FFMPEG_FOUND)
+    ocv_check_modules(FFMPEG_libavresample libavresample) # optional
+    if(FFMPEG_libavresample_FOUND)
+      list(APPEND FFMPEG_LIBRARIES ${FFMPEG_libavresample_LIBRARIES})
+      list(APPEND _used_ffmpeg_libraries libavresample)
+    endif()
+    set(HAVE_FFMPEG TRUE)
+  else()
+    set(_missing_ffmpeg_libraries "")
+    foreach (ffmpeg_lib ${_required_ffmpeg_libraries})
+      if (NOT FFMPEG_${ffmpeg_lib}_FOUND)
+        list(APPEND _missing_ffmpeg_libraries ${ffmpeg_lib})
+      endif()
+    endforeach ()
+    message(STATUS "FFMPEG is disabled. Required libraries: ${_required_ffmpeg_libraries}."
+            " Missing libraries: ${_missing_ffmpeg_libraries}")
+    unset(_missing_ffmpeg_libraries)
+  endif()
+endif()
+
+#=================================
+# Versions check.
+if(HAVE_FFMPEG AND NOT HAVE_FFMPEG_WRAPPER)
+  set(_min_libavcodec_version 54.35.0)
+  set(_min_libavformat_version 54.20.4)
+  set(_min_libavutil_version 52.3.0)
+  set(_min_libswscale_version 2.1.1)
+  set(_min_libavresample_version 1.0.1)
+  foreach(ffmpeg_lib ${_used_ffmpeg_libraries})
+    if(FFMPEG_${ffmpeg_lib}_VERSION VERSION_LESS _min_${ffmpeg_lib}_version)
+      message(STATUS "FFMPEG is disabled. Can't find suitable ${ffmpeg_lib} library"
+              " (minimal ${_min_${ffmpeg_lib}_version}, found ${FFMPEG_${ffmpeg_lib}_VERSION}).")
+      set(HAVE_FFMPEG FALSE)
+    endif()
+  endforeach()
+  if(NOT HAVE_FFMPEG)
+    message(STATUS "FFMPEG libraries version check failed "
+            "(minimal libav release 9.20, minimal FFMPEG release 1.1.16).")
+  endif()
+  unset(_min_libavcodec_version)
+  unset(_min_libavformat_version)
+  unset(_min_libavutil_version)
+  unset(_min_libswscale_version)
+  unset(_min_libavresample_version)
+endif()
+
+#==================================
+
+if(HAVE_FFMPEG AND NOT HAVE_FFMPEG_WRAPPER AND NOT OPENCV_FFMPEG_SKIP_BUILD_CHECK)
+  try_compile(__VALID_FFMPEG
+      "${OpenCV_BINARY_DIR}"
+      "${OpenCV_SOURCE_DIR}/cmake/checks/ffmpeg_test.cpp"
+      CMAKE_FLAGS "-DINCLUDE_DIRECTORIES:STRING=${FFMPEG_INCLUDE_DIRS}"
+                  "-DLINK_LIBRARIES:STRING=${FFMPEG_LIBRARIES}"
+      OUTPUT_VARIABLE TRY_OUT
+  )
+  if(NOT __VALID_FFMPEG)
+    # message(FATAL_ERROR "FFMPEG: test check build log:\n${TRY_OUT}")
+    message(STATUS "WARNING: Can't build ffmpeg test code")
+    set(HAVE_FFMPEG FALSE)
+  endif()
+endif()
+
+#==================================
+unset(_required_ffmpeg_libraries)
+unset(_used_ffmpeg_libraries)
+
+if(HAVE_FFMPEG_WRAPPER)
+  ocv_add_external_target(ffmpeg "" "" "HAVE_FFMPEG_WRAPPER")
+elseif(HAVE_FFMPEG)
+  ocv_add_external_target(ffmpeg "${FFMPEG_INCLUDE_DIRS}" "${FFMPEG_LIBRARIES}" "HAVE_FFMPEG")
+  set(__builtin_defines "")
+  set(__builtin_include_dirs "")
+  set(__builtin_libs "")
+  set(__plugin_defines "")
+  set(__plugin_include_dirs "")
+  set(__plugin_libs "")
+  if(HAVE_OPENCL)
+    set(__opencl_dirs "")
+    if(OPENCL_INCLUDE_DIRS)
+      set(__opencl_dirs "${OPENCL_INCLUDE_DIRS}")
+    elseif(OPENCL_INCLUDE_DIR)
+      set(__opencl_dirs "${OPENCL_INCLUDE_DIR}")
+    else()
+      set(__opencl_dirs "${OpenCV_SOURCE_DIR}/3rdparty/include/opencl/1.2")
+    endif()
+    # extra dependencies for buildin code (OpenCL dir is required for extensions like cl_d3d11.h)
+    # buildin HAVE_OPENCL is already defined through cvconfig.h
+    list(APPEND __builtin_include_dirs "${__opencl_dirs}")
+
+    # extra dependencies for
+    list(APPEND __plugin_defines "HAVE_OPENCL")
+    list(APPEND __plugin_include_dirs "${__opencl_dirs}")
+  endif()
+
+  # TODO: libva, d3d11
+
+  if(__builtin_include_dirs OR __builtin_include_defines OR __builtin_include_libs)
+    ocv_add_external_target(ffmpeg.builtin_deps "${__builtin_include_dirs}" "${__builtin_include_libs}" "${__builtin_defines}")
+  endif()
+  if(VIDEOIO_ENABLE_PLUGINS AND __plugin_include_dirs OR __plugin_include_defines OR __plugin_include_libs)
+    ocv_add_external_target(ffmpeg.plugin_deps "${__plugin_include_dirs}" "${__plugin_include_libs}" "${__plugin_defines}")
+  endif()
+endif()