Modify methods used to access Country currency symbols and codes inside wpsc_format_currency.  Part of larger effort to ensure the theme engine componenet uses the latest methods in WPSC_Country.
First pass at updating theme engine to use new WPSC_Country methods.
It seems that prior to 3.8.14, WPSC_Country::get_all() returned an array of WPSC_Country objects.  It seems to have regressed to now just return an array of countries.  This commit fixes that.