Processed metrics metadata 

The metrics should ideally return all the translations in `getDefaultMetricTranslations()` so a call to `getTranslatedName()` is no longer needed. I am seeing such calls in xhprof quite often. This makes execution much faster (175ms are currently spent in this function on my server) and the HTTP API for `getDefaultMetricTranslations` will then return all translations. If a report wants to overwrote a default translation this should be done in the report class itself as done before.