Refactor C++ version of the Gilded Rose kata

* Make it possible to build and run tests in CLion
  and Visual Studio 2019 out of the box

* Provide four types of initial test using different test frameworks:
  * Catch2 test framework
    * Traditional unit testing using Catch2
    * Approval test using Catch2
  * Google Test test framework
    * Traditional unit testing using Google Test
    * Approval test using Google Test

* The different types of initial test are located in separate folders
  in the test folder.

* Remove scripts to build and run tests and replace
  with instructions in the cpp README.md

* Use C++17

* Use CMake => 3.13

cpp/test/cpp_catch2_approvaltest/GildedRoseCatch2ApprovalTests.cc

@@ -0,0 +1,29 @@
+#define APPROVALS_CATCH
+#include "ApprovalTests.hpp"
+#include "GildedRose.h"
+
+std::ostream& operator<<(std::ostream& os, const Item& obj)
+{
+    return os
+        << "name: " << obj.name
+        << ", sellIn: " << obj.sellIn
+        << ", quality: " << obj.quality;
+}
+
+TEST_CASE("GildedRoseApprovalTests", "VerifyCombinations")
+{
+    std::vector<string> names { "Foo" };
+    std::vector<int> sellIns { 1 };
+    std::vector<int> qualities { 1 };
+
+    auto f = [](string name, int sellIn, int quality) {
+        vector<Item> items = {Item(name, sellIn, quality)};
+        GildedRose app(items);
+        app.updateQuality();
+        return items[0];
+    };
+
+    ApprovalTests::CombinationApprovals::verifyAllCombinations(
+            f,
+            names, sellIns, qualities);
+}