Proposal: Replace single TFA Range input with 3 fields

[megannissel]

From Stacie on Slack:

The Value Range input is ok, but unintuitive. It's workable as is, but i'd have suggested having three inputs, something like "minimum TFA value", "maximum TFA value" and "step value", which are integers, perhaps less prone to typeos, and just seems more clear. As it is, new users must click on the Information button to know what to enter there.