Correctly restore brightness customize dialog hierarchy.

This is especially important when rotating the device.

Change-Id: Iaf1ceb46943e9d0a171d6a75d3d446dbec205095
Improve brightness curve preview

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

Change-Id: Idb6cd2773186f9e7011486dc62f21e2fab85e245

Conflicts:
	res/values/dimens.xml