add population name into Organism.status dictionary

[mauriceling]

1. Currently, Organisms have a deme in the status dictionary, which defines sub-population.
2. However, organisms are not aware of it's original population name.
3. Biologically, an organism can mate between different demes (breeds, races, etc) but not between distinct populations (like between species).
4. When reviving a simulation from database, it is often not possible to know which population it is unless we assume deme as population but that was not the original intention of deme as deme can change within a simulation.
5. Needed to add a population name (from simulation parameters) into Organism.status.

[mauriceling]

1. Database contains population name - create table if not exists organisms (start_time text, pop_name text, org_name text, generation text, key text, value text). Hence, it is possible to get original population with different demes from the database.