Show collisions

[qbi]

Sometimes two or more might collide. It would be nice to show collisions in some other color (red) in the overview page or show colliding entries in the editing page. This makes it easier to detect and resolve them.

[enko]

I think this will be done as a validation. If in the same location on the entered date is an event the user will be presented with an error and a checkbox, so he can create the event never the less, because sometimes the location is so large that it can host multiple events.