Fix tasks #6666: Additional lines are not yellow in artifact link

When you select an artifact to add in artifact link, the corresponding
row is fetched and added to the table report. In experimental theme we
loose the information of a-new-element-is-waiting-for-being-added.

Moved the corresponding rule from the core to the plugin as this class
was only used in trackers. Hopefully.

Change-Id: Ib351df44797d7b9507e9ae1efcb17c86138440de
Merge commit 'refs/changes/76/2276/3' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix tasks #6666: Additional lines are not yellow in artifact link
This is Tuleap 6.12.99.40

Change-Id: I84e79178149cfaf52db50cf4d99f8e9fea3d7031