managing objective value and bounds

[jac0320]

minlp2 is rich with this info for different solvers, while the info is kept independently in a different format. Other libs are limited to fetching the information back.

Just thinking about what this feature should achieve:

• User can know the best objective value/bound of a given instance
• User can access an objective value/bound obtained by some solver with specific configuration
• User can fetch at least be given some details or a ref to some details of the solver configuration with a given objective value/bound entry
• User can access & manage the info with this package without changing the package master branch

[jac0320]

This seems to be a long-term goal as standards can different for each user.