port database layer from appframework to core

lib/private/appframework/db/db.php

lib/private/appframework/dependencyinjection/dicontainer.php

lib/public/appframework/db/doesnotexistexception.php

lib/public/appframework/db/entity.php

lib/public/appframework/db/idb.php

lib/public/appframework/db/mapper.php

...blic/appframework/db/multipleobjectsreturnedexception.php

tests/lib/appframework/db/EntityTest.php

tests/lib/appframework/db/MapperTest.php

tests/lib/appframework/db/MapperTestUtility.php