allow use db functions without table
revert decorators
Merge #5484
Merge branch 'db-sql-select-functions-without-table' of git://github.com/turrsis/zf2 into feature/5484-db-select-without-table

* 'db-sql-select-functions-without-table' of git://github.com/turrsis/zf2:
  revert decorators
  allow use db functions without table
Zend\Db\Sql\Select Fixed variable reference
Close #5484
Merge branch 'feature/5484-db-select-without-table' into develop

* feature/5484-db-select-without-table:
  Zend\Db\Sql\Select Fixed variable reference
  revert decorators
  allow use db functions without table