Added a method to delete the predictions

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka@10647 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Added support for BatchPredictors

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka@10648 e0a1b77d-ad91-4216-81b1-defd5f83fa92