Added some danish books (#3594)

* Added more books

* Updated index

* Changed spacing and headings

free-programming-books-dk.md

 ### Index
 
 * [C](#c)
+* [C#](#c-sharp)
+* [C++](#c-1)
 * [Java](#java)
 * [Pascal](#pascal)
 
@@ -11,6 +13,16 @@
 * [Programmering i C](http://people.cs.aau.dk/~normark/c-prog-06/pdf/all.pdf) - Kurt Nørmark (PDF)
 
 
+### C Sharp
+
+* [Object-oriented Programming in C#](http://people.cs.aau.dk/~normark/oop-csharp/pdf/all.pdf) - Kurt Nørmark (PDF)
+
+
+### C++
+
+* [Notes about C++](http://people.cs.aau.dk/~normark/ap/index.html) - Kurt Nørmark (HTML)
+
+
 ### Java
 
 * [Objektorienteret programmering i Java](http://javabog.dk) - Jacob Nordfalk