Separate includes into sections and alphabetize them

Okay, so basically here's the include layout that this game now
consistently uses:

[The "main" header file, if any (e.g. Graphics.h for Graphics.cpp)]
[blank line]
[All system includes, such as tinyxml2/physfs/utfcpp/SDL]
[blank line]
[All project includes, such as Game.h/Entity.h/etc.]

And if applicable, another blank line, and then some special-case
include screwy stuff (take a look at editor.cpp or FileSystemUtils.cpp,
for example, they have ifdefs and defines with their includes).

desktop_version/src/Graphics.h

@@ -1,21 +1,16 @@
 #ifndef GRAPHICS_H
 #define GRAPHICS_H
 
-#include "GraphicsResources.h"
-#include <vector>
-#include <map>
-
-
-
-#include "Maths.h"
-#include "Textbox.h"
-
-
-#include <string>
 #include <algorithm>
+#include <map>
+#include <string>
+#include <vector>
 
+#include "GraphicsResources.h"
 #include "GraphicsUtil.h"
+#include "Maths.h"
 #include "Screen.h"
+#include "Textbox.h"
 
 class Graphics
 {