customize /etc/issue

add bbappend for base-files to add a customized issue and issue.net
add customized busybox config

* add telnetd (yes! telnetd) and matching init script
* change inetd.conf to start busybox ftpd
* add a bunch of other useful tools
* remove dhcpd
add image-config package

* disable bootlogd
* recommend busybox-ftpd
* require busybox-telnetd and busybox-inetd