This way, if two account values are BALANCE types containing only a
single AMOUNT, then it will do the sorting comparison of the amounts --
since otherwise balances are ignored for the purposes of sorting.
The prices report now uses the following scheme:
PAYEE -> name of commodity of price
ACCOUNT -> name of commodity of item
AMOUNT -> price
DATE -> date of pricing
However, the report does not show the payee. The only reason the payee
is set is to enable clever querying. For example:
ledger prices gold # show all known prices for GOLD
ledger prices @gold # show all known prices *in* GOLD
