Moving all assertions and consistency checking to unit tests

[AtiyahElsheikh]

There are random ad-hoc assertions that are conducted across the code, many of which are excessively executed. It is beneficial in terms of correctness and performance to carry out such checking along unit tests.

Related to #31 #39 #58 #59

[AtiyahElsheikh]

Basics:

• [x] Towns
• [x] Houses
• [ ] Person

After initialisation:

• [ ] verifying that adjacent towns are correct

During simulation:

• [ ] verify that empty (occupied) houses are empty during simulation
• [ ] no homeless
• [ ] verify consistency of towns
• [ ] house occupants are unique
• [ ] consistency between house occupants and occupants
• [ ] consistency between parentship / children, their gender and their age differences
• [ ] Partnership consistency and their genders