precalc UMAP and add row/col reorder buttons

[cornhundred]

Pre-calculate UMAP coordinates for the rows and columns of a heatmap. Save these in the Visualization JSON. If UMAP coordinates are available to Clustergrammer-GL, show UMAP reordering buttons for rows and columns. Pressing the UMAP buttons for rows/columns will cause the matrix to disappear, rows/columns rectangles (viz-aid-triangles) will rearrange (animated ismms-himc/clustergrammer-gl#4) themselves into a UMAP (not zoomable for now). If making a UMAP of columns, then row categories and row names will remain visible. Clicking row categories or rows from the invisible matrix will change the colors of the UMAP squares/points.

[cornhundred]

We're going to integrate spatial data using a separate visualization. See the se examples:

• https://github.com/ismms-himc/visium-clustergrammer2
• https://github.com/cornhundred/citibike-clustergrammer2