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.

This patch has been proposed by Alexis Fidalgo. It was earlier reported
that Kea always appends a dot at the end of the hostname which may cause
some clients to fail on processing this option.

The new tests are implemented using the Dhcp4Client class. It has been
found that the server returns DHCPNAK in response to DHCPDISCOVER which
was wrong. Now, the server doesn't respond to DHCPDISCOVER if it can't
find an address. As a result, a number of tests had to be fixed which
relied on this invalid behavior.