Reorder taxa when selecting/filtering taxa from legend

[nbokulich]

Current Behavior
The taxon selection function (to view specific taxa on a mouse-click) is great, but the selections appear in their original locations instead of aligning with the y-axis origin and appearing in a contiguous bar. If a user wants to zoom in on a few specific groups of interest and re-scale the y-axis to zoom in on these (e.g., for low-abundance taxa), the results will not be pretty.

Proposed Behavior
Selections should start at the y-origin and stack neatly to that users can toggle nice publication-ready figures with minimal data editing.