ls: moved generic URI utilities to uri.c

"ls" is a bad name for a library which parses URIs.  We'll move the
rest of the "ls" library later.

src/command.c

@@ -23,6 +23,7 @@
 #include "playlist_save.h"
 #include "queue_print.h"
 #include "ls.h"
+#include "uri.h"
 #include "directory.h"
 #include "directory_print.h"
 #include "database.h"