Initial basic functionality commit

What this commit adds:
* Ability to apply a theme, given a folder
* Extract all .zip files in /Themes/ into a relevant folder
* Get all theme metadata from info.smdh
* Proper unicode handling

What's still needed for initial release:
* Theme shuffling
* GUI

source/linked_lists.c

@@ -0,0 +1,10 @@
+#include <stdlib.h>
+
+#include "linked_lists.h"
+
+void add_node(node *current, node *new_node)
+{
+	while (current->next != NULL) current = current->next;
+
+	current->next = new_node;
+}