Several improvements (#9)

* fix icon filename

* update pp2d to fix preview problem

* several improvements:
- rely on a single header for simple/common headers
- cleaned up main by putting the interface drawing function in its own file
- load previews from .zip themes (may cause some loading times when launching
- only need 1 shuffle image thanks to pp2d's blending abilities

* not needed anymore

* fix preview color and position

* forgot

* add proper icon loading
thanks steveice10 for bannertool which this was pretty much taken from

* only add proper themes to the list

* add slightly more space between the icon and the name

* not monospace, the little movement every blink is annoying

* fix typo

source/unicode.c

@@ -24,11 +24,6 @@
 *         reasonable ways as different from the original version.
 */
 
-#include <stdlib.h>
-#include <3ds.h>
-#include <string.h>
-#include <stdio.h>
-
 #include "unicode.h"
 
 ssize_t strulen(u16 *input, ssize_t max_len)