- Pkt4::check() removed
 - commented recent change in Pkt4::setType()
 - Pkt4::setType() now used OptionInt<uint8> rather than
   Option::setUint8()

1) Removed the srv-hooks logger
2) Updated DHCP4_NCR_CREATE message description
3) Updated logging doc.

Also, renamed loggers.

Except user guide related and "fixme" leftovers.

Also, revised the debug levels for all messages in the Dhcp4Srv class.

src/bin/dhcp4/dhcp4_srv.cc
    Dhcpv4Srv::assignLease() - added logic to update the lease DB with a
    generated FQDN when not doing a fake allocation

src/bin/dhcp4/tests/fqdn_unittest.cc
    added TEST_F(NameDhcpv4SrvTest, hostnameReservation)

Fixed, copyrights, typos, minor clean up items

doc/guide/logging.xml - added new logger description
src/bin/dhcp4/dhcp4_log.cc - added bad_packet logger and log name declarations
src/bin/dhcp4/dhcp4_log.h - added bad_packet and log name externs
src/bin/dhcp4/dhcp4_messages.mes - changed drop and NAK message identifiers
src/bin/dhcp4/dhcp4_srv.cc - changed packet drop and NAK log invocations
src/bin/dhcp4/main.cc - used extern for log name

Log the ciaddr and requested-ip-address if exists. Previously the message
said it logged yiaddr sent by the client, but the client doesn't set the
yiaddr.

And avoid the excessive use of getQuery/getResponse.