JaGrLib worker modules - descendants of Worker.

@author Josef Pelikan (PE) @version 0.23 $Rev: 75 $ $Date: 2004-04-13 01:01:10 +0200 (Ășt, 13 IV 2004) $ $Author: pepca $ @since 0.23 @see cz.cuni.jagrlib.piece @see cz.cuni.jagrlib.testing @see cz.cuni.jagrlib.obscure