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
Actually, that would make things more complicated, since we have different ways to get pretty names (getRepositoriesNames for repos other than desktop, and this code for components inside desktop:
                $name = (in_array($component, array_keys($components_names)))
                        ? $components_names[$component]
                        : $component;

Also, we can't access $repo in getStatus()