added boost subtraction unit test
add Equality unit test for balance
edited subraction test
add test for multiplication
add unit test for balance division
add unit test negation for balance_t
add unit test Absolute for balance_t
add unit test Ceiling for balance_t
add unit test Floor for balance_t
add unit test Round for balance_t
add unit test Truth for balance_t
add unit test of Zero for balance_t
add unit test printing for balance_t