Fatiha commit méthodes: -void setlocal_currency(Currency currency)
                        -List<Currency> findAvailables()
                        -Map<Currency, AskBid> FindAll()
Fatiha commit: method void delete(Currency currency)
               method Map<Currency, AskBid> FindAll()
               method void setlocal_currency(Currency currency)
               method List<Currency> findAvailables()