Added reference to cryptocurrencies in relevant property descriptions (#1894)
Added reference to cryptocurrencies in relevant property descriptions (#1894)

* Issue (#1866): Added reference to cryptocurrencies in description for 'paymentAccepted' & 'currenciesAccepted' properties.
For consistency, also added to description of properties: 'discountCurrency', 'price', 'priceCurrency', 'currency'.

* Fix typos

* Updated the description additions to reference ISO 4217 formats, cryptocurrency Ticker symbols, LETS and other currency types
including single inline examples for each.

schemaorg/schemaorg,schemaorg/schemaorg,vholland/schemaorg,unor/schemaorg,unor/schemaorg,schemaorg/schemaorg,schemaorg/schemaorg,vholland/schemaorg,unor/schemaorg,vholland/schemaorg,schemaorg/schemaorg,vholland/schemaorg