- 'dhcpd_global_options' text block has been split into individual
variables;
- if list of nameservers is not specified, debops.dhcpd role will
advertise nameservers set in '/etc/resolv.conf' file;
- default set of options can be enabled or disabled using a bool
variable 'dhcpd_auto_options'. The options have been moved to
a separate configuration template included in main one;
