Add default 64x64 scan orders and entropy models

Adds 64x64 default scan orders
Adds 64x64 coefficient entropy models (just copy the 32x32 ones)
Entropy context updates for 64x64 transform
Various misc. changes to support 64x64 transforms

Change-Id: I2c0bc4ba540886dd196e87a78b205407ad3e866b
12 files changed