Boiler capacity is added as dummy decision variable.

The variable is only used to print the value. The variable is not used
in optimization process.
Results of 2 objective are organized
An optimization file for 2 objectives
A problem class for 2 objectives
Two utility file is add

- can take VAR file and simulate every solutions to extract required
parameters (e.g.: production of different units)
- can take VAR file and create two files with feasible solutions (no
constraints violation)