Added memfile without persistence to set_config unit tests. This eliminates
the tests attempting to create the csv file.

Updated copyrights.

Fixed misspelling.

src/lib/config/command_mgr.cc
    CommandMgr::commandReader(int sockfd) - duplicates the connection
    socket to use for repsonding in case the command closes the channel.

src/lib/testutils/io_utils.cc
    fileExists() - now uses stat() function so one can use it on any
    type of file, like a unix socket

updated unit tests accordingly

src/bin/dhcp4/ctrl_dhcp4_srv.cc
    commandConfigReloadHandler() - use commandSetConfigHandler()
    instead of processConfig() to account for logging config

    commandSetConfigHandler() - apply logging config and commit config here instead of
    in processConfig()

src/bin/dhcp4/tests/dhcp4_test_utils.h
     ~NakedDhcpv4Srv() - removed unecesary initLogger call

src/bin/dhcp4/tests/kea_controller_unittest.cc
     ~JSONFileBackendTest() - removed unecessary call to setDefaultLogging

src/bin/dhcp6/ctrl_dhcp6_srv.cc
    commandConfigReloadHandler() - use commandSetConfigHandler()
    instead of processConfig() to account for logging config

    commandSetConfigHandler() - apply logging config and commit config here instead of
    in processConfig()

src/bin/dhcp6/tests/ctrl_dhcp6_srv_unittest.cc
    createUnixChannelServer() -  added config commit so command channel behavior
    is correct

    TEST_F(CtrlDhcpv6SrvTest, configReload)
        Wrap configuration in Dhcp6 element

    TEST_F(CtrlChannelDhcpv6SrvTest, set_config)
        Turn off timers in config

src/lib/dhcpsrv/srv_config.cc
    SrvConfig::applyLoggingCfg() - remove logic added to not call manager.process
    when there are no specs.

    Mirror the changes made in kea-dhcp6.

src/lib/dhcpsrv/srv_config.cc
    SrvConfig::applyLoggingCfg() - now only calls LoggerManager::process()
    if the logger config isn't empty

src/bin/dhcp6/ctrl_dhcp6_srv.cc
src/bin/dhcp6/tests/dhcp6_test_utils.cc
    Minor clean up and commentary

src/bin/dhcp6/kea_controller.cc
    configure(const std::string& file_name)
    - Removed initial rollback, now done in commandSetConfigHandler()

src/bin/dhcp6/tests/ctrl_dhcp6_srv_unittest.cc
   - Removed unnecessary call to initLogger

src/bin/dhcp6/ctrl_dhcp6_srv.cc
    ControlledDhcpv6Srv::commandSetConfigHandler()
    - Add logger config
    - Use processConfig() directly instead of config-reload command

src/bin/dhcp6/kea_controller.cc
    configure(const std::string& file_name)
      - Remove logger config
      - Use set-config command instead of config-reload

src/bin/dhcp6/tests/ctrl_dhcp6_srv_unittest.cc
    createUnixChannelServer()
    - added call to initLogger() to revert logging to unit test logger

src/bin/dhcp6/tests/dhcp6_test_utils.cc
    BaseServerTest::~BaseServerTest() {
    - added call to initLogger() to revert logging to unit test logger

src/bin/dhcp6/ctrl_dhcp6_srv.h
src/bin/dhcp6/ctrl_dhcp6_srv.cc
    ControlledDhcpv6Srv::commandSetConfigHandler() - new method to process
    the set-config command.

    ControlledDhcpv6Srv::processCommand() - call new set-config handler

    ControlledDhcpv6Srv::processConfig() - added logic to apply logging
    and commit configuration after  successful reconfig

    ControlledDhcpv6Srv::ControlledDhcpv6Srv(uint16_t port) - added registration
    of set-config command

    ControlledDhcpv6Srv::~ControlledDhcpv6Srv() - unregisters set-config command

src/bin/dhcp6/json_config_parser.cc
    configureCommandChannel() - extracted logic to reconfigure command channel
    to its own fucntion

src/bin/dhcp6/kea_controller.cc
    configure() - removed logic to apply logging and commit config, now done
    in ControlledDhcpv6Srv::processConfig()

src/bin/dhcp6/tests/ctrl_dhcp6_srv_unittest.cc
    TEST_F(CtrlChannelDhcpv6SrvTest, set_config) - new test to exercise the
    set-config command

# Conflicts:
#	src/lib/dhcpsrv/pool.h

src/bin/dhcp6/dhcp6_srv.h
src/bin/dhcp6/dhcp6_srv.cc
    Removed unused ctx parameter from Dhcpv6Srv::appendRequestedOptions()

Trivial changes.