* [Commands] Add #setaltcurrency Command.
- Add #setaltcurrency [Currency ID] [Amount] command to allow you to set a specific alternate currency to a value.
- Add Zone::GetCurrencyID() and Zone::GetCurrencyItemID() helper methods.
- Cleanup loops through zone->AlternateCurrencies.
- Utilize helper methods where necessary.
- Convert old methods parameters and return values from int to uint32 where necessary.
* Typo.
