[3341] Allow b10-dchp-ddns to optionally support updates in a given direction

Added methods to D2CfgMgr to return whether or not forward or reverse
updates are enabled. Altered D2UpdateMgr::makeTransaction to utlilize
these new methods. Added additional logs and unittests.
[3222] Augmented DNS message IO in b10-dhcp-ddns

Added descriptive message comment log statement for
to outbound DNS update requests, and conversion of status
and RCODEs for DNS inbound responses to b10-dhcp-ddns log.
[3222] b10-dhcp6 now controls D2ClientMgr

Added D2ClientMgr send mode control and error handler
to Dhcp6vSrv and use of each to ControlledDhcpv6Srv.
Added new unit test files d2_unittest.h and cc.
[3222] b10-dhcp6 now sends NCRs to b10-dhcp-ddns

Replaced use of internal queue in Dhcpv6Srv with posting
NCRs to D2ClientMgr. Upgraded unit tests accordingly.
b10-dhcp6 is now fully able to participate in DDNS.
[3222] Made b10-dhcp-ddns server matching case insensitve

The method used in D2 to match a FQDN (or reverse IP addrss)
to a list of servers, DdnsDomainListMgr::matchDomain(), was
made case insensitive.
[3222] Added D2 unit test files to dhpc6
[3222] Removed superflous server instance in dhcp6 unit tests

Added a member instance of NakedDhcpv6Srv to FqdnDhcpv6SrvTest
rather than have an external local instance for each test.
[3222] Fixed a few nits found during the review.
[2367] Move experimental resolver config code to the top of configure.ac
[2367] Rename AM conditional variable
[2367] Update help message
[2367] Add configure arguments for enabling/disabling DNS and DHCP components
[2367] Conditionally include DNS and DHCP components (use AM conditionals)
[3222] Addressed review comments, augmented logging

In addition to minor corrections, unit tests for NameChangeTransaction::
responseString was added.  Also added a similiar method NameChangeTransaction::
transactionOutcomeString() and unit tests.
[3343] Classification is now done before calling accept()
[3343] ChangeLog updated.
[3353] One line fix for eRouter1.0 client class processing
[master] Merge branch 'trac3222'

b10-dhcp6 fully able to do DHCP-DDNS
[master] Added ChangeLog entry 762 for Trac #3222
[3341] Addressed review comments.

Improved doxygen commentary for new methods.