Use `Currency` type in tx metadata details

[mvadari]

Currencies that aren't 3 letters are still hex in this output.

Example:

(Ideally, the first line would read It deleted a XRP/MB589 offer node owned by rBjBZPghaXLmNmgzU1gYi5UEfwinJEjcja with sequence #69545115)

The Description section has the same problem:

https://livenet.xrpl.org/transactions/5AA36C90A9337F876B2C89270AE705A941333D5DACBF9F4199592F71AE1CC604/detailed