Min/max demands: Implement minor fixes and tests

Updated the input format and problem description files to reflect the demand constraint changes

Updating the product demand to per-center rather than system-wide

Format build.jl

Adding product demand constraints

model: Capacity cannot decrease over time

model: Fix division by zero

Fix RELOG.parsefile

Reformat source code

Implement plant storage

Implement plant expansion

Implement _add_pwl_constraints

docs: Minor fix

Add emission limits and penalties

Implement plant emissions