fix perl tests for modify callback fix
add missing test dependencies
another missing build dependency
added --trackLabel and --key options to prepare-refseqs.pl
make storage backend backcompat guessing  smarter: pay more attentoin to urlTemplate file extensions rather than track types
make default mismatch color be gray, so we can see any mismatch text
parse CIGAR before MD in mismatches, so the MD mismatches will be rendered on top of the CIGAR ones.  also, look for "md" in the feature, which is more compatible than "MD"
update release notes