- `tooltip` takes the name of a GeoJSON property that will be
shown in a tooltip when hovering the mouse over a feature.
- `popup` can take either the name of a property as above, or
the boolean value `true`. In the latter case, a table of all
the feature's properties will be shown when clicking on the
feature. In the former case, only the value of the designated
property will be shown.
- Now a layer may consist of a path pointing to a directory plus a
glob, or a path pointing directly to a single file.
- If a file already exists in the database, check if the layer
name has changed and if so, update it.
- Do not import the actual file contents, as the path is enough
(it can be retrieved via the /file/:path API endpoint).
