Squash auto-brightness updates

Overhaul auto-brightness level UI.

This changes a few things:
- Don't imply a 'bucket' type of algorithm is used by showing an ambient
  brightness range for each line
- Allow manually entering the screen brightness
- Add a preview window for the cubic spline interpolation
- Add a help text

JIRA:CYAN-612
Change-Id: I64274280872b9fe4f6fdc368d654aca81e0a4e0c

Improve brightness curve preview

- Avoid log spamming
- Add a little margin around the grid so outer control points aren't cut

Change-Id: If4dabdf4c713e01e59a0f367f6e95772ebc12cd7

Correctly restore brightness customize dialog hierarchy.

This is especially important when rotating the device.

Change-Id: I345823cb0a4fb30bd8ecdf40d241e2e6a394ae0a