Warns the user that it is a lab mode feature

Part of story #7577 display a Kanban cardwall

Change-Id: Idb5f65851fc6578f67edab79477c3f248f0fb03a
Merge commit 'refs/changes/37/3337/2' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Warns the user that it is a lab mode feature

Change-Id: Iddf004852643573e907ba866d26a5f0615892a91
This is Tuleap 7.7.99.71

Change-Id: I59e2611f2abd1764aad18e6cf81520b5f0af3483