Increases number of wedges for smaller block and removes
wedge coding mode for blocks larger than 32x32.

Also adds various other enhancements for subsequent experimentation,
including adding provision for multiple smoothing functions
(though one is used currently), adds a speed feature that decides
the sign for interinter wedges using a fast mechanism, and refactors
wedge representations.

lowres: -2.651% BDRATE

Most of the gain is due to increase in codebook size for 8x8 - 16x16.

Change-Id: I50669f558c8d0d45e5a6f70aca4385a185b58b5b