several issues in DvTime

[Sergio Miranda Freire]

Argument magnitudeStatus is missing in the initializer and in the call to the superclass initializer.
magnitude is an derived attribute, so it does not need to appear as an argument in the initializer.

DvDate inherits from DvAbsoluteQuantity and ISO8601Time (support package). So it is necessary to implement all methods of both classes, namely:
      add, subtract, diff, compare, isStrictlyComparableTo (DvAbsoluteQuantity)
     asString, hour, minute, second, hourUnknown, minuteUnknown, fractionalSecond, hasFractionalSecond, timezone, secondUnknown isPartial, isExtended, isValidISO8601Time, isDecimalSignComma (ISO8601Time) and enforce the invariants:
Hour_valid: valid_hour(hour, minute, second)
Minute_valid: not minute_unknown implies valid_minute(minute)
Second_valid: not second_unknown implies valid_second(second)
Fractional_second_valid: has_fractional_second implies (not second_unknown
and valid_fractional_second(fractional_second))
Partial_validity: minute_unknown implies second_unknown