epurdom
Improve "-1" (unassigned) color assignment in plotTracking
Currently, the code for plotTracking treats "-1","-2" as any other cluster for the purposes of aligning the clusters and giving them colors, and then does a post-processing change to the color so that the "-1"/"-2" get the right color.
A better solution is for the internal ordering/alignment to treat them differently. For example, if the first row assigns cluster "12" to color "blue", and then a large number of "-1" in the second row align to this blue cluster, the "-1" cluster will get assigned "blue" which only later gets converted to "white" in post-processing. The end result is a cluster in the second row which is not "-1" and has the next most overlap with "blue" cluster in the first row doesn't get assigned "blue" but another color (and no cluster in the second row gets assigned "blue").
