Improve message center card formatting

- [x] Improve the display of long message titles:

![Screenshot_20190703-140842](https://user-images.githubusercontent.com/5524043/61662284-f7862380-ac82-11e9-80d9-4138966d4762.png)

- [ ] Contain embedded objects within the card to prevent overflow:

![Screenshot_20190917-084526](https://user-images.githubusercontent.com/5524043/65057711-ddd22700-d927-11e9-9a8f-cfb01abb71e4.png)


