src/bin/dhcp4/dhcp4_lexer.ll
src/bin/dhcp4/dhcp4_parser.yy
    Added parsing support for config-control and config-databases

src/bin/dhcp4/json_config_parser.cc
    configureDhcp4Server() - added handler for config-control element

src/bin/dhcp4/parser_context.*
    added CONFIG_CONTROL and CONFIG_DATABASE

src/bin/dhcp4/tests/config_parser_unittest.cc
   TEST_F(Dhcp4ParserTest, configControlInfo) - new test