Allow modification of the optimization problem after creation

Currently the ETS code builds an integer linear programming problem from the given inputs and determines an optimized solution. This solution can then be analyzed whether it produces fiber collisions during the movement stage. If such events are detected, it is desirable to be able to alter the problem configuration and re-run the optimization, hopefully without a complete restart.

I'm preparing a change that exposes the LP variables and constraints in the problem to the user so that they may change their parameters even after optimization and then re-run the optimizer.