Stats per language and project

Right now statistics are only available from the dashboard, and they cover the whole instance.
For consistency, building community within a language, and the usefulness of reaching out to translators when something needs to be done urgently, it would be nice to see statistics in the language tab, and also per project.

The call for also having per project based statistics went something like this:

Lets say someone wants to reach out to the top translators for any given project. It could be that there are a lot of other translators, that just translate other projects, and have no interest in translating the one project in question.

Start by locating the existing dashboard statistics and the language and project tab entry points. Determine how statistics should be scoped to a language or project, then verify that each view reports the appropriate translators and totals without changing instance-wide statistics.

Written by the indexing model from the issue text.