 - Fixed getTime() for negative durations.  - Added negate() method for easy negation of durations (i.e. for subtracting a duration)
 - Fixed getTime() for negative durations.
 - Added negate() method for easy negation of durations (i.e. for subtracting a duration)

ical4j/ical4j,tschaible/ical4j,ariordan/ical4j,amannm/ical4j,tschaible/ical4j,voronaam/ical4j,voronaam/ical4j,amannm/ical4j,ariordan/ical4j,ical4j/ical4j,tschaible/ical4j,voronaam/ical4j,ariordan/ical4j,ical4j/ical4j,amannm/ical4j