added feature to rename a host

[da-]

conf zone <whatever> modify host will now accept rename to change the host name.

Note that renaming preserves all other data, such as CNAME aliases.

An extended example:

user@ib.domain.name > show host foobaz.domain.name
                       aliases : other.domain.name
             configure_for_dns : true
                     ipv4addrs : 10.11.12.13
                          name : foobaz.domain.name
                  network_view : default
                   rrset_order : cyclic
                         views : External
                          zone : domain.name

user@ib.domain.name > show host quux.domain.name
  Error : API returned : The specified object was not found (1003)

user@ib.domain.name > conf zone "" modify host foobaz.domain.name rename quux.domain.name

user@ib.domain.name > show host quux.domain.name
                       aliases : other.domain.name
             configure_for_dns : true
                     ipv4addrs : 10.11.12.13
                          name : quux.domain.name
                  network_view : default
                   rrset_order : cyclic
                         views : External
                          zone : domain.name
user@ib.domain.name >