Filter now never removes the class. Fixed bug where class was removed when it matched the regular expression but inversion of selection was turned on.

git-svn-id: https://svn.cms.waikato.ac.nz/svn/weka/trunk@10394 e0a1b77d-ad91-4216-81b1-defd5f83fa92
Merge remote-tracking branch 'upstream'