Make add always reset the country

Before, add reset the country only when adding a player or a visitor.
When adding a deity or deleting a country, it set just nat_cnam,
nat_pnam and nat_state.  Has always been that way.

Because of that, a newly minted deity country could inherit all kinds
of crap from a previous user of its country number: origin, realms,
relations, telegrams, ...  Harmless if the country number has never
been used before, which is how add is generally used.

When adding a deity country, initial levels (start_education, ...) now
apply, relations start NEUTRAL instead of AT_WAR, and the usual
initial nation flags are set.

Reset on delete as well, just to get rid of the special case.