Rename get_jobs() to get_total_jobs in Building and Building_datum.  New functions, Building::get_available_jobs() and Building::get_filled_jobs().
Citizens struct tracks how many of its population are employed; new function Citizens::get_unemployed() returns the differents between population and employment.  Move Citizens constructor (and new destructor) to city.cpp.  New function, City::get_unemployed_citizens().  New functions City::employ_citizens() and City::fire_citizens() add and remove citizens from a specified building, and do all the accounting etc. necessary, after several checks to make sure these are legal operations.
Right-align some fields.
More work on Interface::minister_food().  It's (almost?) done!  You can now assign/remove crops from the farm(s) of your choice.  Food grown isn't updated since City::get_food_production() isn't written yet...