Add a button to add an event

[xavez]

We might need a button to add an event from the sidebar (not on the calendar)

Less priority because people eventually find how to add an event.

[Bertware]

Added button, just needs to be hooked in to javascript. Button only visible when logged in.

[mietcls]

The button that says “voeg event toe”, it’s just as prominent as export. Make them switch places and make the export button a little less prominent (a secondary button), so it won't stand out so much.

This is an example, but ask @brucevansteenwinkel for a secondary button.

[xavez]

Fixed. Great!