bugfix: ResultSet#getXXX(String) requires not columnName but columnLabel.

DefaultEntityOperator uses columnName from ResultSetMetadata to get
value from ResultSet.  Though ResultSet's get operation requires
columnLabel.
Merge pull request #15 from dai0304/use_getColumnLabel_instead_of_getColumnName

bugfix: ResultSet#getXXX(String) requires not columnName but columnLabel...