Add dashboard / summary list of events

[gn36]

A dashboard that summarizes all events of the week (aggregate from topics) and allows yes / no / maybe votes.

This is more of a long-term idea with a lot of work involved but also containing probably a lot of useful features if the hookup is mainly used for finding participants for fixed event dates.

• Dashboard
  • aggregate all events
  • allow changing / updating entries from dashboard
  • Use forums as "tags" for sorting the dashboard
• Allow customization of the dashboard in the ACP
  • allow custom tags per event
  • configure default tags per forum
  • configure default visibility of entries
    • all future dates in the list
    • only topics with only one list
    • only topics with a fixed date
• Allow customization of the dashboard in the UCP
  • configure default tags to be visible
  • configure tag lists to be visible
  • configure visibility of entries
    • all future dates in the list
    • only topics with only one list
    • only topics with a fixed date
• Ical export of the dashboard list