Implement custom notification level options
![Screen_Shot_2016-06-17_at_15.31.43](/uploads/3fc47d2f461b3e8b67bb8acaa304cf99/Screen_Shot_2016-06-17_at_15.31.43.png)
![Screenshot_from_2016-06-15_10-52-27](/uploads/88dbdd21d97e80ee772fe08fa0c9b393/Screenshot_from_2016-06-15_10-52-27.png)
part of #12758
See merge request !4389