Set initial layer color trough datasource-properties.json

[normanrz]

It would be nice to set the color of a layer in the datasource-properties.json. I still think the users should be able to edit that color, but this could be the default.

[philippotto]

Ok, I gave this some thought and I think, we should extend the datasource-properties.json with all default-view-related properties. That is, position, zoom, segmentationOpacity and interpolation (for the dataset) as well as color, alpha and intensityRange (per layer).
The back-end should read these settings from the datasource-properties.json file and return them when the view configuration is requested from the front-end.

To stay backwards-compatible with existing view-configurations which are not controlled via the datasource-properties.json, we still keep the View Configuration settings. If they are empty, the back-end reads the properties from the disk. If they were changed, the new values are written to the DB and then read from there.

Do you agree, @fm3?

[fm3]

well we have to save those things somewhere on the wk side (amongst the rest of the „datasource“ properties, since the json itself is only available for the datastore). but I guess we can maybe afford to duplicate this in the db. what do you think @youri-k ?