Analytics tab in the admin section

We should re-integrate repository analytics, search analytics and workflow analytics dashboards. Concerning the workflow analytics dashboard, we should re-think it so that it is a bit more generic than the default one we have, in order not to have to contribute a dashboard for each workflow instance, but on the contrary to be able to browse the analytics of a given workflow model with the same html code.

We should also add in this section the ability to browse / search for any audit log entry.