use Converter to convert data array to/from entity object.
(not entity object but entity array, now.)
after a second thought, give created|updated field as text.
extracted interfaces for Dao.
still __call for Query builder is annoying.
remove unused attribute in Dao.
only datetime format is necessary; date and time uses the same format.
make a method as protected.
update, not insert for modDatum.
specify returning object for @method.
correctly get setter/getter method name.
add phpdocs.