Switched to using align_* (align_mismatch, etc.) for styling of (non-feature) divs for SNVs in DraggableAlignments track. Also made previous insertion/deletion/substitution style rules specific to sequence alterations in WebApollo SequenceTrack to avoid namespace collision.
Revised DraggableAlignments to improve rendering. 
Copied and modified _drawMismatches from Alignments superclassk. Should really refactor in Alignments so don't have to do cut-and-paste, or DraggableAlignments changes should get moved over to Alignments. By default rendering of SNVs (mismatch, insertion, deletion) for DraggableAlignments is now handled in _drawMismatches as non-feature divs, rendering of match regions is handled as normal subfeature divs, and skips are not rendered. Also, drawing residues for mismatches is turned off by default, can turn on using config.showMismatchResidues, but will still not draw residues unless read alignments feature div height is tall enough to fit the residues font.