Added an option to specify whether the values of string attributes should be retained in memory when reading incrementally.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka@11071 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Added an option to specify whether the values of string attributes should be retained in memory when reading incrementally.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka@11072 e0a1b77d-ad91-4216-81b1-defd5f83fa92