Express characteristics of the Wallet as part of the interface

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Some aspects of the wallet should be reflected in the interface. Ex:

• currency code for the coins
• does the wallet/coin support time-based redemption scripts
• maximum coin divisibility (magnitude of smallest fraction of coin)

This data might be represented via a func Config() *wallet.Properties where

type wallet.Properties struct{
 CurrencyCode string
 FeatureTimeBasedRedemptionScripts bool
 MaximumDivisibility uint
}