support date as well as datetime in Balance.value()
support date as well as datetime in Balance.value()

cargo-cut'n'paste from py_amount.cc

ledger/ledger,ledger/ledger,jwakely/ledger,paulbdavis/ledger,paulbdavis/ledger,jwakely/ledger,jwakely/ledger,afh/ledger,duncanmortimer/ledger,jwakely/ledger,duncanmortimer/ledger,duncanmortimer/ledger,afh/ledger,afh/ledger,jwakely/ledger,paulbdavis/ledger,paulbdavis/ledger,duncanmortimer/ledger,ledger/ledger,paulbdavis/ledger,duncanmortimer/ledger,jwakely/ledger,afh/ledger,jwakely/ledger,duncanmortimer/ledger,paulbdavis/ledger,ledger/ledger,ledger/ledger,paulbdavis/ledger,afh/ledger,duncanmortimer/ledger