Make sure that all references to layer are removed when layer is deleted

[jacobwod]

Currently when we remove a layer from the layer repository, we also take a look in all map configs and remove the layer's ID from each map's LayerSwitcher options.

Since 22d648e it is possible to also add WMS layers as search sources. In that case the layer's IDs are added to an Array of Search tool's options (searchSources). When we remove a layer from the repository we must also ensure that the possible references to the layer are removed from searchSources, or else we'll have orphaned references left which will cause a crash when loading the Search tool.