…djustable-thresholds

This reorganizes bag storage such that bags are always referred to
by their upper threshold. This in turn means that adding and removing
bags is cheaper; you only need to migrate certain voters, not all of them.

The macro approach seems to be a non-starter; that only really works
if we're throwing around numeric literals everywhere, and that's just
not nice in this case.

Instead, let's write helper functions and make it really easy to
generate the tables in separate, permanent files, which humans
can then edit.

This isn't yet done, becuase it seems to take a Very Long Time to run,
and it really shouldn't. Need to look into that.

Still, it's a lot closer than it was this morning.

Turns out that when you're working in exponential space, you need
to divide, not subtract, in order to keep the math working properly.

Also neaten up the output a little bit to make it easier to read.