relative measures: attainment or shortfall?

[alysonvanraalte]

We would like to implement an argument to give users the option of defining whether the following should be based on attainment (achieved_age) or shortfall distributions (remaining_life), (e.g. distribution_type = c("remaining_life", "achieved_age")).

• Theil
• MLD
• CoV
• H
• Gini