Reset default logistic curve values to flat

[chrisnatali]

Otherwise HH demand is variable and confusing if not thought through

[carbz]

Explicitly, we've converged on these values throughout IDN and MMR work: 1.0 1.0; 1000.0 1.0; 100000.0 1.0; 1000000.0 1.0
such that the Demand model's default should read as such:
default = '1.0 1.0; 1000.0 1.0; 100000.0 1.0; 1000000.0 1.0'
across all categories with logistic curves. This is the easiest fix.

But really, I'd vote to just eliminate these logistic curves multipliers altogether from the model since they're confusing and we never use them anymore in practice. They add unnecessary abstractions to our work's methodology.