Change behavior of how DELETE action works

[ykevu]

When a cell is deleted, the cell is deleted from the cells.json array, but the value in the labeledArray does not change. This has resulted in a number of visual bugs, such as those that make it appear like deleted cells are still there; the bugs are, to my knowledge, mostly fixed, but future bugs and the kind of weird workarounds can be prevented if this behavior is fixed. Note that there is a bit of nuance since if that cell overlaps with another cell, deleting it should not make all values go to 0; there needs to be checks for this sort of case.