MAX_TILE experiment: add explicit tiles

This patch is designed to complete the CONFIG_MAX_TILE experiment.
It adds the following features:
- Explicit tiles of same width can be signalled with command line --tile_width
- Explicit tiles of same hieght can be signalled with command line --tile_height
- max_tile now works with the depenedent horizontal tiles experiment
- additional checking added to ensure maximum number of rows/columns <= 64
- one fix to the tile group code for when the number of tiles is not a power of two

Change-Id: I749a68fdb3dcdd8d1ced2b3558f3817e4b832c06