TRDS: Dark DocumentsUI

for Downloads app

PS:
- fix settings

Change-Id: I87d49e97b8a0a67bd4d85f0137eb0960155428cb

Conflicts:

	packages/DocumentsUI/AndroidManifest.xml
	packages/DocumentsUI/res/layout/activity.xml
	packages/DocumentsUI/res/layout/fragment_save.xml
	packages/DocumentsUI/res/layout/item_doc_grid.xml
	packages/DocumentsUI/res/values/colors.xml
	packages/DocumentsUI/res/values/styles.xml