resolves #34 - add code block formatting for Java

[tobiasbueschel]

I've left f6451f8 & 0898245 attached to this commit as the code formatting block addition references the new filename.

Here is a picture of how the code will look like:

[tobiasbueschel]

It might be nice if we could implement the above using markdown's code notation (this way we comply with the idea of writing only markdown) and get the same syntax highlighting as when using the LaTeX command, e.g.:

System.out.println("hello");

Instead of

\lstinputlisting[style=javaCodeStyle, caption=Main.java]{source/code/HelloWorld.java}

Then again, using LaTeX for importing code from files is quite powerful, so we might just stick with this option?