System message UI tweaks

- Add action-sheet-class option for action sheet directive
- Enable scrolling in system messages action sheet
- Partial fix for https://github.com/Rise-Vision/common-
header/issues/396
- Change "System Messages" title to "Notifications", fix for
https://github.com/Rise-Vision/common-header/issues/395
- Sort system messages, fix for https://github.com/Rise-Vision/common-
header/issues/393
- Add more fake test message to test, in combination with https://github.com/Rise-Vision/gapi-mock/pull/8
Merge pull request #398 from settinghead/master

System message UI tweaks