return the presentation time that matches the current client wall clock time

this may not be the live edge since the client wall clock time is
different from the server wall clock time
ensure that playback starts at the startTime
don't use duration if it is NaN
converts the mpd time to utc time
replaces isLive with isDynamic
adds one-time tasks triggered at a given video/wall time  to RequestScheduling
renames event listeners in StreamController
takes into account start time of the first period in StreamController.getStreamForTime
adds dash vo objects to cache the data derived from manifest
changes timeline calculation logic by using vo objects and timelineConverter in DashHandler
prevents manifest updating until the previous update is completed
removes duration rounding in DashHandler.isMediaFinished
sets liveEdge for SegmentTimeline videos
cleanup
prevents playback start before the player buffers enough data
fixes seeking issue
fixes liveEdge calculations
fixes dataChange flag resetting in BufferController
fixes DashMinifestExtensions.getDuration
update wowza live mpds