Move Mediawiki stastistics computation in the plugin

Dear developer, events and plugin hooks are there for a good reason.
DRY: Do not duplicate the construction of mw databases name

Change-Id: I92517e6e4ea5f3f2ebceef4c361ccc65fc94eb8f
Merge commit 'refs/changes/67/467/2' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  DRY: Do not duplicate the construction of mw databases name
  Move Mediawiki stastistics computation in the plugin

Change-Id: I0774f9dadeda61eb67c5def32c414ea4ce4e27ef
Tuleap 6.1.99.14

Change-Id: I8e34d03edaa89b43b2e9f4e132528cea66d44a26
Fix changelog

Change-Id: I73001db9afb9f327ed5edc3e18244522e43e26fb