Add "!" to old shields

Show old shields on portals with exclamation mark.
The old series of shields had mitigation values of 6, 8 and 10 (now it's 10, 20 and 30).

A preview of the list, the obsolete shields have "S!".
![image](https://f.cloud.github.com/assets/219708/841919/61764186-f3a1-11e2-9555-d5cef0f52ad7.png)
Maybe it would be useful to find some better style to highlight the old mods.