[3089] D2UpdateMgr now uses NameChangeTransaction derivations

Now that NameAddTransaction and NameRemoveTransction classes
have been implemented, D2UpdateMgr has been updated to use
them.  It now creates instances of NameAddTransaction and
NameRemoveTransaction based on the change type specified in
received NameChangeRequests as designed.
[3089] Corrected log argument in d2::NameAddTransaction
[3234] Subnet-id is now set properly in b10-dhcp{4,6} servers
[3231] Implemented test fixture class to run tests with fake interfaces.
[3231] Set fake interface for the incoming packet in DHCPv4 unit tests.
[3231] Dynamically generate server identifier and append to server response
[3231] Removed fixed server identifier option from the DHCPv4 server.
[3231] Removed the source address adjustment of the packet in LPF.

The DHCPv4 server is now responsible for setting up a correct unicast
source address for the outgoing packet. The IfaceMgr doesn't replace
the broadcast address with the unicast address anymore.
[3231] Updated bind10-guide to accomodate dynamic generation of server id.
[3033] Added DHCP-DDNS configuration paramater parsing to b10-dhcp4

Added configuration paramters to dhcp4 and its spec file to support DHCP-DDNS.
Created new classes D2ClientMgr, D2ClientConfig, and D2CientConfigParser in the
libdhcpsrv.   The new parameters are parsed, validated, and stored  but do
not yet affect behavior.  That will be implemented as a seperate ticket.
[3033] Corrected doxygen errors in dhcpsrv
[1033] Add unittest for log layout pattern
[1283] Define operator<< for IOAddress
[1283] Remove toText() calls where IOAddress should be used directly
[1444] Make DATASRC_SQLITE_DROPCONN message more admin-friendly
[3231] Corrected a typo in dhcp4_srv.h
[2347] Add missing <functional> include

This seems to be required on certain platforms (Visual Studio 2012) to
use std::bind1st, std::not_equal_to, etc. On other platforms, it may
have been transitively included.
[571] Don't print trailing newlines in Question::toText() output by default

It is possible to get the old behavior by passing toText(true).

Message::toText() output is unchanged.
[3234] Changes after review:

 - ChangeLog updated
 - Current reconfiguration limitations described in User's Guide
 - Dhcp{4,6}ParserTest.reconfigureRemoveSubnet added
 - Subnet::getNextID -> generateNextID
 - Various comments improved
[3231] Implemented function which checks if the v4 packet is relayed.