Refactor optimization result and objective classes + add preliminary support for...

Refactor optimization result and objective classes + add preliminary support for multiple objectives (#6459)

This PR is one part of multiple.
Preliminary support means currently only supports single objective.
It supports queue-ing up objectives and it always optimizes the first.
Multiple-obj optimization algorithm will be up next.

*  Refactor optimization result and objective classes
*  Add preliminary support for multiple objectives
* The unit tests are now comparing node values instead of node addresses