grouper: Better background gradients

Now lots of backgrounds look a bit ugly.
Using another dithering mode produces better gradients

Change-Id: I1907f02cb3c0c96ae7337d9eda17e7b39bf86db7
Implemented F2FS for use on /data

Based on commit 4776c688c705b46925f9c9e1e6daf09692519fcf of Google's
Tegra 3 kernel for the 2012 Nexus 7.

Patches thanks to Now Computing's f2fs-backports repo:
https://github.com/nowcomputing/f2fs-backports/