This patch refactors the DST transforms so that the orthonormal and
 asymmetric transforms are now nearly identical (up to multiplicaiton
 constants and an extra set of shifts).
This means that the DST designs are now embeddable for every level
 and should address hardware concerns about gate area.

In addition, minor changes were made to improve transform accuracy:

 - all of the transforms now have perfect reconstruction for those
    computations outside the rotations, i.e., all +/- butterfly steps
    are exactly invertible
 - two multiplication constants were reduced below < 1.0 (better for
    SIMD and gives slightly improved accuracy)
 - the averaging bias is removed which saves an extra addition for each
    of the averaging steps

Additional averaging steps can be removed from the 8-point Type-IV DST
 giving a 68% reduction in MSE for the 32-point DCT, but has not been
 done in the event we use it in place of the 8-point Type-VII DST.

subset-1:

master-daala_tx@2017-12-10T22:38:19.651Z ->
 new-daala_tx@2017-12-10T22:37:50.844Z

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
0.0057 | -0.0210 | -0.1821 |   0.0085 | -0.0002 |  0.0147 |    -0.0674

Change-Id: Ib124eebf6f2e4b3c51c078d4e8f229fc5ec26171