minor [util\excel] fix unit test output buffer
minor [db\orm] fix unit tests
feature [db] add Query support for sql GROUP BY, HAVING, WITH ROLLUP
feature [validatation] add support for NULL values, skipping other validators
fix [orm] fix Repository create(), execInsertOne(), execUpdateOne() casting array values with DataMapper::array2object()
tests [orm] add tests with nullable properties
feature [validator, orm] add support for NULL values
feature [orm] add Repository FETCH_JSON mode
Merge branch 'develop'