The message of the day functionality was heavily depended on
components of Gerrit core. In Gerrit-3.0 only the extension point was
left of this feature, but it wasn't used anywhere to actually display
the messages registered with it. While this feature was reenabled for
the PolyGerrit-UI in Gerrit 2.16, for compatibility reasons, it still
depended on the components in Gerrit core. It is planned to move this
functionality completely to the plugin. Since it was not usable with
the new UI for a long while, the functionality will be removed
completely until then.
Change-Id: If653e7042db981e55d08fa29e14dd9201fb22627
5a89a55940