[1/2] Lockscreen notifications enhancements

- Make multi-user aware
- Disable proximity related options by default
- Reorganise settings
- Fixed possible NPE
- Fixed NPE on devices without navbar

Add option to:
- Enable/disable if notification is actually dismissed
- Force enable low priority notifications

Modifications by @Evisceration:
- Possible NPE fixes
- Optimize notification addition process

Change-Id: I11bca31d21891a41d00841d1c6c3b5421b091309
Filter Notifications : Adjust string

Change-Id: I797cef15fcbd2ebca1d411a71cae75aaf3b478f1