Do not pass aufs 'dirs=' option to /etc/fstab

These don't work on remount and cause systemd-remount-fs.service to
fail.
Use 'dhclient' instead of dhcpcd

It is easier to control with its dhclient.conf
DHCP configuration improvements

– use vendor-class-identifier of "pld-new-rescue:$version", so we can
make DHCP server configuration for PLD NR only
– stop network started in initramfs, so wicd can start from scratch
– option to keep the early udhcpc running in case we need constant
network connection (e.g. for future iSCSI boot)
– wicd configuration updated to make sure it will automatically start
the wired connection
typo
README.md: formatting fixes
iSCSI boot support added

allows 'Minimum RAM' PXE boot