Hide expired events after 2 weeks from end date

[yankedev]

After some time, expired events are not so important anymore to be immediately loaded in the dashboard list.
To speed up rendering of the page with a lot of events (above 20), expired events should be loaded with a separate call and be graphically hidden (open a sub-list to view all of them)

[yankedev]

for expired events it can also be interesting to see number of sold tickets directly in the list (or some additional info)

[cbellone]

see also #186

[syjer]

Todo:

• currently the cutoff date is exactly the expiration date, is the 2 week time lag a good idea?
• show sold tickets/places statistic

[syjer]

done :)