Add CI and HI for plan evaluation

[Gourav Jhanwar]

Create methods for evaluating the Conformity Index and Homogeneity Index in the Plan Evaluation class.

[Gourav Jhanwar]

Methods added in Evaluation class. Users can use methods pp.Evaluation.get_conformity_index(my_plan, sol=sol), pp.Evaluation.get_homogeneity_index(my_plan, sol=sol) to get CI and HI respectively