Update portuguese tranlation (by altiereslima).

Added Bulgarian translation.

Fixed: multiple applying the pollution radius and road slope multipliers in case the game is reloaded.

Added Korean and Chinese translations.
Fixed: Loan amount and length are multiplied cumulatively every time the game is loaded.

1) Compatibility with Natural Disasters DLC.

2) Some balance fixes for the highest difficulties.

Update for the nl, de and it translations.

Revised economy ballance.

Bug fix

Added Maximum Slope option.

Added French locale.