Use diamond search to build tpl model and arf frames

Use diamond search to build tpl model and arf frames

Use diamond search for full pixel motion estimation to build
the temporal dependency model and the source arf frame. This gives
better full pixel motion estimation accuracy. It improves the
compression performance.

In speed 0,
         avg PSNR     overall PSNR     SSIM
midres    -0.32%        -0.30%        -0.65%
hdres     -0.88%        -0.91%        -1.31%
nflx2k    -0.47%        -0.48%        -0.81%

In speed 1,
        avg PSNR      overall PSNR     SSIM
midres    -0.24%        -0.28%        -0.50%
hdres     -0.82%        -0.83%        -1.18%
nflx2k    -0.58%        -0.60%        -0.89%

The encoding speed change is minor due to the fact that such motion
estimation is triggered once at the beginning of each group of
picture coding.

Change-Id: Ib25c0ff4f7450c85fd7a38d24319bd7ae1b9dac8