Fix deprecated set calls

This PR fixes installation issues caused by the deprecation of WPSC_Country::get(), WPSC_Country::save(), and WPSC_Country::exists(), discussed in #1053

I had to call WPSC_Country::_save_country_data() externally once on line 55 of 2.php in order to change the ISO code of the country.

There are likely other issues caused by calls to deprecated functions, I'll keep looking.