Settings: customizable slim lockscreen background (2/2)

- color fill (with transparency slider)
- custom image  (with transparency slider)
- full transparent
- default

This Settingspart containes a small comment change for Notificationbackground settings

Patchset 2: cleanup

Change-Id: I6542dd72b02a9fcdbf1159fa95ba64fcfc75796e

	modified:   res/values/pa_arrays.xml
	modified:   res/values/pa_strings.xml
	modified:   res/xml/lock_screen_settings.xml
	modified:   src/com/android/settings/paranoid/Lockscreen.java
	new file:   src/com/android/settings/widget/SeekBarPreference.java

https://github.com/temasek/android_packages_apps_Settings/commit/aa742e3bf2950aeaab92ab42d4142df28092eb5a