src/hooks/dhcp/mysql_cb/mysql_cb_callouts.cc
    load() - added call to register MySQL backend
    unload() - added call to unregister MySQL backend

src/hooks/dhcp/mysql_cb/mysql_cb_dhcp4.*
    MySqlConfigBackendDHCPv4::registerBackendType()
    MySqlConfigBackendDHCPv4::unregisterBackendType()
    - new static methods for registering/unregistering

src/hooks/dhcp/mysql_cb/tests/Makefile.am
    mysql_cb_dhcp4_mgr_unittest.cc  - new file

src/lib/config_backend/base_config_backend_mgr.h
    bool unregisterBackendFactory(const std::string& db_type)
    - new method to unregister factory and delete backends

src/lib/config_backend/base_config_backend_pool.h
    void delAllBackends(const std::string& db_type)
    - new method to delete all backends of a given type

/src/lib/config_backend/tests/config_backend_mgr_unittest.cc
    TEST_F(ConfigBackendMgrTest, unregister) - new test

src/lib/dhcpsrv/Makefile.am
src/lib/dhcpsrv/config_backend_dhcp4.h
src/lib/dhcpsrv/config_backend_dhcp4.cc
    New files that implement ConfigBackendDhcp4Mgr

src/lib/dhcpsrv/config_backend_pool_dhcp4.h
    Added missing public scope, removed pure virtual function

src/lib/eval/tests/Makefile.am
    Added new dependency libkea-cc