Applied all fixes related to translating C to C++ code

Also fixed some typos and code alignment
Also adapted tutorial CPP samples
Fixed some identation problems

samples/cpp/video_dmtx.cpp

@@ -52,7 +52,7 @@ namespace
             if (frame.empty())
                 break;
             cv::Mat gray;
-            cv::cvtColor(frame,gray,CV_RGB2GRAY);
+            cv::cvtColor(frame,gray,COLOR_RGB2GRAY);
             vector<string> codes;
             Mat corners;
             findDataMatrix(gray, codes, corners);