[Workbench] Displays content at the top of the dashboard, set by the sysadmin
Functional requirements: a sysadmin can write arbitrary Textile to appear at the top of the Dashboard page. Workbench displays this content immediately under the top bar.
The idea is that this content would be brief: a basic introduction of what Arvados is used for at this site, or notice of scheduled downtime. With that in mind, the display isn't expected to interfere with the Dashboard's main functionality.