Fix Bug 716497, improve correlations tab ui

@rhelmer Ok, so as mentioned on IRC this is phase 1 of this PR that involved only the correlations tab on report/list

If this is all good, I will amend this PR to also include the same tab on report index.
You can push all of that into jQuery with something like:
```javascript
var table = $('<table><thead><tr>' +
   '<th>All Crashes for OS</th>' +
   '<th>All Crashes for Signature</th>' + 
   '<th>' + type + '</th>' + 
   '</tr></thead></table>');
```