rd: remove unnecessary sbaccoder loads
cutree: Enable CUTree for ratecontrol when tune=ssim and bug fix for cutree

1. added cutree into cli option, default cutree is disabled
2. --tune=ssim then aq and cutree is enabled
3. Fixed bug in slicetype-frameCostRecalculate()
   the qp offset for B and B-REF from lowres qpAqOffset, for non-B from lowres qpoffset
4. Fixed bug in Ratecontrol-getQScale - the clip duration should (frameduration * timescale)
   when cutree is enabled
encoder: increase precision for SSIM printf