Extend to 256 Q steps.
This commit extends the number of Q steps to 256 from 128. The q_trans array has been altered to distribute available Q index values (using the current 64 steps available as input parameters) evenly across the available range. This is coupled with the fact that each Q step where possible now equates to a fixed % change in the quantizer. This may want refinement later especially in terms of the granularity at the high quality end but is a reasonable starting point. Change-Id: I2aaa6874fa10ce05c958dd182947ce39f6f1eecb