Added ISK exchange rate

	modified:   wallet/src/de/schildbach/wallet/ExchangeRatesProvider.java
	modified:   wallet/src/de/schildbach/wallet/WalletApplication.java
	modified:   wallet/src/de/schildbach/wallet/service/BlockchainServiceImpl.java
	modified:   wallet/src/de/schildbach/wallet/ui/WalletActivity.java