ts: refactor OpenCV tests

- removed tr1 usage (dropped in C++17)
- moved includes of vector/map/iostream/limits into ts.hpp
- require opencv_test + anonymous namespace (added compile check)
- fixed norm() usage (must be from cvtest::norm for checks) and other conflict functions
- added missing license headers

modules/dnn/test/test_caffe_importer.cpp

@@ -45,11 +45,7 @@
 #include <opencv2/core/ocl.hpp>
 #include <opencv2/ts/ocl_test.hpp>
 
-namespace cvtest
-{
-
-using namespace cv;
-using namespace cv::dnn;
+namespace opencv_test { namespace {
 
 template<typename TString>
 static std::string _tf(TString filename)
@@ -525,4 +521,4 @@ TEST(Test_Caffe, FasterRCNN_and_RFCN)
     }
 }
 
-}
+}} // namespace