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, related to https://github.com/Rise-Vision/common-header/pull/398
- 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