Add a shortcute for /eval.sh

Create /eval_base64.sh to overcome quoting and newline limitations.

Documente poweroff's failure on readme.

kernel_module/user/poweroff.c

@@ -1,6 +1,6 @@
 /* Userspace is for the weak. Die.
  * https://stackoverflow.com/questions/28812514/how-to-shutdown-linux-using-c-or-qt-without-call-to-system
- * BusyBox's /sbin/poweroff is under init/halt.c, but it does extra crap like killing init, so I don't trust it. */
+ **/
 
 #include <stdio.h>
 #include <sys/reboot.h>