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/gapi/doc/30-implementation.markdown

@@ -0,0 +1,29 @@
+# Implementation details {#gapi_impl}
+
+[TOC]
+
+# G-API Implementation details
+
+Note -- this section is still in progress.
+
+# API layer {#gapi_detail_api}
+
+## Expression unrolling {#gapi_detail_expr}
+
+## Parameter marshalling {#gapi_detail_params}
+
+## Operations representation {#gapi_detail_operations}
+
+# Graph compiler {#gapi_detail_compiler}
+
+## ADE basics {#gapi_detail_ade}
+
+## Graph model representation {#gapi_detail_gmodel}
+
+## G-API metadata and passes {#gapi_detail_meta}
+
+# Backends {#gapi_detail_backends}
+
+## Backend scope of work {#gapi_backend_scope}
+
+## Graph transformation {#gapi_backend_pass}