Add .gitignore and IntelliJ IDEA project configuration files and projects for cpp intro, pointers and classes

cpp/classes/main.cpp

@@ -0,0 +1,17 @@
+#include "ClassA.h"
+
+int main() {
+    ClassA a;
+    a.Print();
+
+    ClassA* pA = nullptr;
+    pA = new ClassA();
+    pA->Print();
+    // (*pA).Print(); // same as above, but more complex to write
+    delete pA;
+    pA = nullptr;
+
+    a.CompareTo(pA);
+
+    return 0;
+}