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/src/CMakeLists.txt

@@ -0,0 +1,4 @@
+set(SRC_LIB_NAME src)
+add_library(${SRC_LIB_NAME})
+target_sources(${SRC_LIB_NAME} PRIVATE GildedRose.cc)
+target_include_directories(${SRC_LIB_NAME} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

cpp/src/GildedRose.cc

@@ -0,0 +1,80 @@
+#include "GildedRose.h"
+
+GildedRose::GildedRose(vector<Item> & items) : items(items)
+{}
+    
+void GildedRose::updateQuality() 
+{
+    for (int i = 0; i < items.size(); i++)
+    {
+        if (items[i].name != "Aged Brie" && items[i].name != "Backstage passes to a TAFKAL80ETC concert")
+        {
+            if (items[i].quality > 0)
+            {
+                if (items[i].name != "Sulfuras, Hand of Ragnaros")
+                {
+                    items[i].quality = items[i].quality - 1;
+                }
+            }
+        }
+        else
+        {
+            if (items[i].quality < 50)
+            {
+                items[i].quality = items[i].quality + 1;
+
+                if (items[i].name == "Backstage passes to a TAFKAL80ETC concert")
+                {
+                    if (items[i].sellIn < 11)
+                    {
+                        if (items[i].quality < 50)
+                        {
+                            items[i].quality = items[i].quality + 1;
+                        }
+                    }
+
+                    if (items[i].sellIn < 6)
+                    {
+                        if (items[i].quality < 50)
+                        {
+                            items[i].quality = items[i].quality + 1;
+                        }
+                    }
+                }
+            }
+        }
+
+        if (items[i].name != "Sulfuras, Hand of Ragnaros")
+        {
+            items[i].sellIn = items[i].sellIn - 1;
+        }
+
+        if (items[i].sellIn < 0)
+        {
+            if (items[i].name != "Aged Brie")
+            {
+                if (items[i].name != "Backstage passes to a TAFKAL80ETC concert")
+                {
+                    if (items[i].quality > 0)
+                    {
+                        if (items[i].name != "Sulfuras, Hand of Ragnaros")
+                        {
+                            items[i].quality = items[i].quality - 1;
+                        }
+                    }
+                }
+                else
+                {
+                    items[i].quality = items[i].quality - items[i].quality;
+                }
+            }
+            else
+            {
+                if (items[i].quality < 50)
+                {
+                    items[i].quality = items[i].quality + 1;
+                }
+            }
+        }
+    }
+}

cpp/src/GildedRose.h

@@ -0,0 +1,24 @@
+#include <string>
+#include <vector>
+
+using namespace std;
+
+class Item
+{
+public:
+    string name;
+    int sellIn;
+    int quality;
+    Item(string name, int sellIn, int quality) : name(name), sellIn(sellIn), quality(quality) 
+    {}
+};
+
+class GildedRose
+{
+public:
+    vector<Item> & items;
+    GildedRose(vector<Item> & items);
+    
+    void updateQuality();
+};
+