Many-to-many blob-measure relationship gets lost somehow.

[brettviren]

@HaiwangYu finds something has caused the many-to-many blob-measure relationship to become separated so that no blobs share measures. This was found in the charge solving tests so the issue occurs somewhere before that.

This happens pervasively for all time slices in his test and he provides the activities in the first time slice of his event to reproduce.

https://www.phy.bnl.gov/~yuhw/wcp-porting-img/pr210/activity-blob-active-tick0.log

These include both 3-view and 2-view. Initial focus is on the MaskSlice:slicing-uboone-ms-active_0 sample.

[brettviren]

One thing found is that the representation of blob corners is effected by floating point uncertainty and the ambiguity that 60 degree wires cause. Every corner has three equivalent representations using any two of three views: (l2,l3), (l3, l4) or (l4, l2). This causes some redundant points to be named and some small change leads to different representations included in the blob corners list. It would be good to clean this up but so far I don't think it's related to the issue.

[brettviren]

Fixed in #214