IC: Slow down

Miguel (Research Assistant in Musicology for the _ECHOES Project_) has noticed a slow down in the IC when clicking on **grouping** and **splitting**, and **when clicking on a neume it also took longer to get the right place in the page and highlight it**. As this was not the case when we started from scratch, he thinks that his might be due to the number of glyphs we have on the training data (around _7,000 glyphs_). But I don't know why the training data would affect the speed of grouping and splitting actions. It is true that when splitting glyphs, these moved from a particular class to `UNCLASSIFIED`; and I think that, when grouping glyphs, they should share a class first. But, I really don't think that the number of examples in training data should affect the grouping and splitting actions.

I don't know if this issue is a slowdown related to an "IC issue" or a "Rodan issue."

@JoyfulGen, @kyrieb-ekat, and @annamorphism have you noticed this behaviour before?

I am also tagging @fujinaga here to keep him up to date and @elsinhadl.