Modifies the scanning pattern and uses a floating point 16x16
dct implementation for now to handle scaling better.
Also experiments are in progress with 2/6 and 9/7 wavelets.

Results have improved to within ~0.25% of 32x32 dct for std-hd
and about 0.03% for derf. This difference can probably be bridged by
re-optimizing the entropy stats for these transforms. Currently
the stats used are common between 32x32 dct and dwt/dct.

Experiments are in progress with various scan pattern - wavelet
combinations.

Ideally the subbands should be tokenized separately, and an
experiment will be condcuted next on that.

Change-Id: Ia9cbfc2d63cb7a47e562b2cd9341caf962bcc110