Should it be possible to create events without a place?

[david-ziegler]

this might be necessary for example for online summits etc. But then: how do we show them in kartevonmorgen.org? Should they always appear in search results? But that could be confusing for someone who wants to see only events in the current map view. Or we could show them under "Entries outside the current map view", which we already have now. Or should we just not allow events without a place?