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_unittest/CMakeLists.txt

@@ -0,0 +1,15 @@
+set(TEST_NAME GildedRoseCatch2UnitTests)
+add_executable(${TEST_NAME})
+target_sources(${TEST_NAME} PRIVATE GildedRoseCatch2UnitTests.cc)
+target_link_libraries(${TEST_NAME} lib src)
+set_property(TARGET ${TEST_NAME} PROPERTY CXX_STANDARD 17)
+add_test(NAME ${TEST_NAME} COMMAND ${TEST_NAME})
+
+# Set compiler option /FC for Visual Studio to to make the __FILE__ macro expand to full path. 
+# The __FILE__ macro is used by Catch2 to get the path to current test file.
+# Links:
+# * https://docs.microsoft.com/en-us/cpp/preprocessor/predefined-macros?view=vs-2019
+# * https://docs.microsoft.com/en-us/cpp/build/reference/fc-full-path-of-source-code-file-in-diagnostics?view=vs-2019
+if (MSVC)
+    target_compile_options(${TEST_NAME} PRIVATE "/FC")
+endif()

cpp/test/cpp_catch2_unittest/GildedRoseCatch2UnitTests.cc

@@ -0,0 +1,12 @@
+#define CATCH_CONFIG_MAIN  // This tells Catch to provide a main() - only do this in one cpp file
+#include "Catch.hpp"
+#include "GildedRose.h"
+
+TEST_CASE("GildedRoseUnitTest", "Foo")
+{
+    vector<Item> items;
+    items.push_back(Item("Foo", 0, 0));
+    GildedRose app(items);
+    app.updateQuality();
+    REQUIRE("fixme" == app.items[0].name);
+}