Settings: add safe headset volume and less annoying sound notification

Add settings for both features.

Change-Id: I8ab4f4b9ec320238b05ac51fb76ac24b93c37d37
(cherry picked from commit 5d8d5cfaec835f7a4168131c1a508aa71bd788dd)

Conflicts:
	res/values/cm_plurals.xml
	res/values/slim_strings.xml
Option to use volume keys to control media volume anytime [2/2]

The volume keys control the Media volume rather than the Ringer
hence removing the issue of accidentaly changing the Ringer volume.

Credits: Pawitp

Change-Id: Ic0a1c04ae41eac65e9535d6de5f11c0456730315

Conflicts:
	res/values/cr_strings.xml

(cherry picked from commit 82e813263298ab084a1f428489b3ea2fcd5a23b9)