Dashboard widget display (OSOE-541)

[Piedone]

Ideas by @MikeAlhayek and @sebastienros:

• Have a dashboard widget available, when OrchardCore.AdminDashboard is enabled (and then not display the simple insertion.
• Make the values we use available as Liquid tags, and build the widget as a Liquid widget. That way, you can customize it but still get a default.

Jira issue