Import Classifier now imports the feature lexicon, too.
Got rid of all traces of the 'Change Feature Lexicon' feature.  Changed the JLabeldata methods for setting the feature lexicon.  Fixed some bugs.
Hopefully fixed JLabelData:importClassifier() so that it tries very hard to make the import work, but tells the user immediately if the import fails.  Also added a couple methods that do most of what JLabelData:UpdateStatusTables() does, but without changing the object state at all.
Refactored UpdateStatusTable into the bits that don't change the object state, and the bits that do.