…gs to startFrame and lastFrame.

    --ff FIRSTFRAME       Set the first frame of the viewer
    --lf LASTFRAME        Set the last frame of the viewer
    --cf CURRENTFRAME     Set the current frame of the viewer

* Refactored setFrame to _setFrameIndex
  * Removed the closestFrame lookup - as far as I'm aware this does nothing of value as closestFrame always equals frame.
    * This has given us a speed increase on playback - the closestFrame lookup iterated over the entire _timeSamples list every time the frame changed.
  * Removed the need for the forceUpdate variable.

* Re-purposed setFrame to be a simple wrapper that finds a frameIndex and calls _setFrameIndex.

* Found bug where resetting of the timeline would also not update the dataModel - so the value on the timeline and what was being shown in the viewer would not match up.
  * This was fixed by adding a call to setFrame in _UpdateTimeSamples