Currency serialization

[microposmp]

Made a small change to the serialization of PricePart data. Currently data for the unspecified currency is stored.

	"PricePart": {
		"Price": {
			"value": 999.0,
			"nativename": "Unspecified",
			"englishname": "Unspecified",
			"symbol": "---",
			"iso": "---",
			"currency": "SEK"
		}
	},

Added it to the currency table to make it known and serialize like this.

	"PricePart": {
		"Price": {
			"value": 99.0,
			"currency": "SEK"
		}
	},

[bleroy]

Thanks!