[1/3] base: Notifications settings

Added changes from:

https://gerrit.omnirom.org/#/c/5734/

Original developer: David96<xd_e-mail@gmx.de>

Modifications of OmniROM:
- Dynamic width control: Schubi <schubi@erlangen.ccc.de>
- Control whether notifications should be dismissed or not
& Force include apps with low priority notifications when
  hide low priority is enabled: Utkarsh Gupta <utkarsh.eminem@gmail.com>
- Integration into OmniRom Notifications Settings: Juan Ezquerro Llanes <arrase@gmail.com>

Big changes incoming and only want to maintain one PS :)

Change-Id: I87fc59ad1e3bc01c08506ae8437bbed2bb3ef419