Implement Health Status view, fixes #306

Initial PR.

To follow up:
- list localizers with https://github.com/pascalchevrel/list_localizers (per repo/per year, and globally for the locale) And maybe globally for all locales
- Improve view performances (cache)
- Fix getStatsPaneDP test (currently disabled)
- Shall we remove code for http://transvision.mozfr.org/showrepos/ or both views should coexist?
- Last commit is most of the times from L10n Drivers, even on Desktop
- Shall we merge in the UI some of the components on Desktop?
- Prettify UI
for both this function and addTab, I think code it's much easier to read if you switch to double quotes as string delimiters.
```
$link .= "><a href='#{$anchor}'>{$title}</a></li>\n";
```