Theme modification to allow for customisations of experimental theme without overwriting

Change-Id: I98b50384a7855de105ed87575404684d78941720
Updating the error message on the forum for anon users

Change-Id: Ib57095a37a122219c29dbf525238759058820d8f
Merge commit 'refs/changes/79/1979/3' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Updating the error message on the forum for anon users
  Theme modification to allow for customisations of experimental theme without overwriting

Change-Id: I1a95daaaa409cc11172653671ea537415e66d82e
This is Tuleap 6.10.99.42

Change-Id: I023e4500b75075178eeb621b8d7c7bb83ee190d2