Rm useless init.sh, init_hello and poweroff are not init specific, so rename them more generically

kernel_module/user/poweroff.c

@@ -0,0 +1,12 @@
+/* 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>
+#include <unistd.h>
+
+int main(void) {
+	puts(__FILE__);
+	reboot(RB_POWER_OFF);
+}