Economic health window fix; new resources window shortcut; production fix for Eritrea and Somalia; limit export volume to production

- Fixed the display of the GDP index in the economic health window.
- New resources window shortcut: When switching the Drugs resource from
public to private automatically privatizes all legalized resources and
sets their tax to 25% if they're primary, or 30% if they're secondary or
tertiary.
- Readjusted the GDP/production fix for Eritrea and Somalia.
- When production is recalculated for each country, its export volume is
restricted to be less than or equal to how much they produce.