Launch music player on headset connect

Tweaked using SystemCheckBoxPreference

Squashed Settings: Add summary for launch music app when headset is connected
Author: jackmu95
https://github.com/CyanogenMod/android_packages_apps_Settings/commit/79924823535f2faae77f186dfed12bc26aa5220b

Launches the default music player when a headset is connected

Patchset 2 - Add headset category
Patchset 3 - Remove summary

Change-Id: I1ee973bec35d95285a646b86213ced3dd15852ed

Conflicts:
	res/values/strings.xml
	res/xml/sound_settings.xml
	src/com/android/settings/SoundSettings.java
Use SystemCheckBoxPreference for volume_adjust_sounds

Also make headset true by default