Added option to toggle between filtering to display just plus strand annotations, just minus strand annotations, or both.  Needs further work on filter implementation in HTMLFeatures, because tiers aren't resizing to shrink when plus/minus strand annotations filtered out.
Added option to toggle between filtering to display just plus strand annotations, just minus strand annotations, or both.  Needs further work on filter implementation in HTMLFeatures, because tiers aren't resizing to shrink when plus/minus strand annotations filtered out.

erasche/Apollo,erasche/Apollo,erasche/Apollo,erasche/Apollo,erasche/Apollo