Last change to ClassifierSubsetEval broke RaceSearch - fixed.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka/trunk@9790 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Added an option to set a threshold on the minimum improvement in merit needed for an attribute to be added from the ranking, and an option to exclude non-improving attributes when considering further additions from the ranking.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka/trunk@9791 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Merge remote-tracking branch 'upstream'