model consistency checking

[AtiyahElsheikh]

There is ad-hoc consistency checking within many functions, e.g. assertions.

Goal is to enhance the library with functions for validating the consistency of the model variables at any time step.

[AtiyahElsheikh]

Some inconsistencies and bugs have been identified and corrected in population initialisation, cf. #59

Some other checks to carry at initial population level

• [x] consistency of kinship relationship
  • [x] partners
  • [x] parent-children relationship
• [x] houses are occupied by singles or families
  • [x] a single person lives alone
  • [x] families live together
  • [x] occupants of a house constitute a family or an individual

It is desired to carry out such verification under unit tests, cf. #60