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/KeyPoll.cpp

@@ -1,11 +1,13 @@
 #include "KeyPoll.h"
-#include "Game.h"
-#include "Graphics.h"
-#include "Music.h"
+
 #include <stdio.h>
 #include <string.h>
 #include <utf8/unchecked.h>
 
+#include "Game.h"
+#include "Graphics.h"
+#include "Music.h"
+
 void KeyPoll::setSensitivity(int _value)
 {
 	switch (_value)