add unit test Absolute for balance_t
add unit test Absolute for balance_t

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