Remove non-currency fields from ImportedVoucher

@billrob @mmorris-gc 

So if we remove the decimal fields from the ImportedVoucher object, this doesn't produce any side effects / compile errors in the latest version of Standard (eastwood), as far as I can tell. 

@mmorris-gc, if it's ok with you, Bill and I would like to remove the decimal? fields from the SDK object.  The actual response from the API will still have these decimal fields intact, but we're going to remove them from the SDK to encourage the use of the new fields.