Move lockscreen buttons options to one place

When you enter "Button actions" you expect to find unlock
options there, not in "Screen security -> Additional options".
Before: http://goo.gl/mX9DMQ
After: http://goo.gl/hPDKyt

Conflicts:
	res/xml/security_settings_cyanogenmod.xml
	res/xml/security_settings_password.xml
	res/xml/security_settings_pin.xml
	src/com/android/settings/SecuritySettings.java

Change-Id: I0e03cdbd6abdb05f1936f9c472807bc30649cdd8