Filter on modelrevision is no longer reliable

[lexvand]

In https://github.com/nens/fews-3di/blob/master/fews_3di/simulation.py#L243 the threedimodel is retrieved based on a contains filter on the slug. This is no longer reliable as the slug no longer contains a unique_id of the revision. Instead it contains the revision number. This has changed after the Klondike release of 3Di.

For example filtering on 'model-name-1' could give multiple results, i.e. 'model-name-10', 'model-name-11' et cetera.

We should change this to an exact filter on the id of the threedimodel.