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/stitching/test/test_blenders.cpp

@@ -41,8 +41,7 @@
 
 #include "test_precomp.hpp"
 
-using namespace cv;
-using namespace std;
+namespace opencv_test { namespace {
 
 TEST(MultiBandBlender, CanBlendTwoImages)
 {
@@ -76,3 +75,5 @@ TEST(MultiBandBlender, CanBlendTwoImages)
     double psnr = cvtest::PSNR(expected, result);
     EXPECT_GE(psnr, 50);
 }
+
+}} // namespace