Addressed review comments for !980.

src/bin/dhcp4/tests/fqdn_unittest.cc
src/lib/dhcpsrv/tests/ncr_generator_unittest.cc
    Added missing test parameter comments

kea-dhcp<4/6> now populate NameChangeRequest::conflict_resolution_
with the appropriate value.

src/bin/dhcp6/dhcp6_srv.cc
    Dhcpv6Srv::createNameChangeRequests() - set use conflict resolution
    in explictly created NameChangeRequest

src/lib/dhcpsrv/ncr_generator.cc
    queueNCRCommon() - added use_conflict_resolution parameter

    queueNCR(const NameChangeType& chg_type, const Lease4Ptr& lease)
    queueNCR(const NameChangeType& chg_type, const Lease6Ptr& lease)
    - set conflict resolution flag from lease's subnet

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

src/bin/dhcp6/tests/fqdn_unittest.cc
    TEST_F(FqdnDhcpv6SrvTest, noConflictResolution)

src/lib/dhcpsrv/tests/ncr_generator_unittest.cc
    udpated  to create subnets and attach them to leases

    TEST_F(NCRGenerator6Test, useConflictResolution)
    TEST_F(NCRGenerator4Test, useConflictResolution)
    - new tests

 - created new table with supported RAI suboptions
 - added RFCs 3011, 3993
 - removed outdated reference do 1497 from limitations section

- replaced all occurences to old_cltt and old_valid_lft in unittests
- renamed syncInternalTimestamp to syncExistingLifetime and changed order
of parameters
- renamed updateInternalTimestamp to updateExistingLifetime
- updated doxygen
- added extra check for all occurences of deleteLease (either call
EXPECT or ASSERT), and only use cast to void if explicitly specified
- updated ChangeLog
- updated old_cltt and old_valid_lft on fromElementCommon and added
unittests
- throw exception with different message on memfile with persitence
disabled for easier debugging