Add support for sequence.nextval in the sql export tool

JDBC's prepared statement provides a feature to include sequence.nextval as a string literal in the select statement. This option is provided since prepared statement does not provide any support for passing a value of sequence.nextval through a binding parameter.

The current version of sqoop export does not provide a feature to include sequence.nextval in the column attribute.

Without this option, it becomes very difficult to generate surrogate keys and hadoop framework does not provide any support out of the box for generating unique/surrogate keys.

It will be of great help to add this feature to sqoop query export tool.