Fixed issue #325, bug that was causing mismatches/insertion/deletions occuring past a skip to not be rendered.
Problem was in _mdToMismatches().nextRecord() method, attempting to use mismatch.len instead of mismatch.length was causing mismatch.start to be set to NaN.
Simplified add_bam_track.pl, removed confusing options.
Made add_bw_track.pl default to setting config.autoscale => local
Renamed add_bam_track.pl to add-bam-track.pl and add_bw_track.pl to add-bw-track.pl to be
consistent with other JBrowse scripts.
Forcing recalc of stripe width at full zoom, since maxPxPerBp can change.
Removed config.subfeatures, and determining whether store should create subfeatures based on config.style.showSubfeatures.