Improve screen timeout QS tile

 * Use com.android.internal.R.plurals.duration_* for text
 * Use white icon as suggested here https://jira.cyanogenmod.org/browse/CYAN-3769

Change-Id: Idfedbc1e7a857dbfa05736810e09528852c8bfa3
(cherry picked from commit 507df14635f0cb840d8ed629529e03e074f88538)

Conflicts:
	packages/SystemUI/res/values/cm_strings.xml