Lockscreen Notifications: Use switch instead of checkbox to toggle feature

Our other features (Active Display, Appbar, etc.) all use a switch to enable/disable. This makes things consistent.

PS2: Whitespace, re-ordering, and set default as false

Change-Id: I28336e6656fa568f5de039ee01a4259ece0feacc
Signed-off-by: Tianrui Guo <tianrui@pac-rom.com>
Merge "Lockscreen Notifications: Use switch instead of checkbox to toggle feature" into pac-4.4