Fix DHCP lease directory name in Debian

Both Debian 6.0 and 7 use /var/lib/dhcp instead of dhcp3.
Use sudoers.d in Debian

Debian 6.0+ have sudoers.d enabled by default. Use it so that the
provisioners (like Chef) don't need to agree on using "sudo" group, or
know anything about "vagrant" user if it manages the /etc/sudoers file.
BENTO-112 add single-request-reopen to resolv.conf
Merge pull request #162 from tmatilai/debian-dhcp

Fix DHCP lease directory name in Debian
Merge pull request #163 from tmatilai/debian-sudoers

Use sudoers.d in Debian
Merge pull request #165 from rjocoleman/single-request-reopen

BENTO-112 add single-request-reopen to resolv.conf
Updated paths and names to version 7.4

:bomb: since there is currently no debian 7.4 image available at
http://cdimage.debian.org/debian-cd/ checksums need updating before this
templates are of any use
Updated ISO checksums according to new iso images