fixed various issues

-fixed crash when switching varieties in Varieties view
-improved performance of switching varieties in Varieties view
-improved performance of switching variety pairs in Variety Pairs view
-fixed selection of incorrect variety after removing a variety
global correspondences view now includes complex segments
segments view now includes complex segments
split vowel and consonant similar segment settings
changed sonority scale to be more fine-grained
renamed Sense to Gloss in find dialog, changed Gloss to default