In visualizations, don't repeat if conclusion is all constants (low priority)

[david-a-wheeler]

In visualizations, if the concluding justification is all constants, then the resulting statement shouldn't be repeated because it adds no new information. E.g., if you visualize df-2, you see:

---------------------
|- 2 = ( 1 + 1 )
|- 2 = ( 1 + 1 )

There's no point in showing it twice, because there are no variables to map to. Being able to show the visualization is great even in this case, because it reveals that this conclusion really is all constants... we just don't need that duplicated.

[expln]

@david-a-wheeler This is fixed on dev.

[expln]

This is available in version 15 https://expln.github.io/lamp/v15/index.html