-isBiallelic would incorrectly say triallelic sites are biallelic.
-getAlternateAlleleList was broken, since the new cached list is immutable, we couldn’t remove list items.
Also added a dbSNP validating walker to the one-offs, for testing the new b37 130 dbSNP rod.
git-svn-id: file:///humgen/gsa-scr1/gsa-engineering/svn_contents/trunk@2568 348d0f76-0448-11de-a6fe-93d51630548a