Merge vector_layer entry method with layer entry method

[dbauszus-glx]

The vector_layer entry and mvt_clone entry type should essentially work the same but are quite different at the moment.

The vector_layer doesn't support themes.

There is a lot of duplicate code which is hard to maintain.

The layer entry method replaces the mvt_clone method. #1268

This method however does not allow for layer queries without the layer already being defined in the workspace.

The vector_layer entry method should be deprectated in support of the layer entry method once it is possible to load layer data from a layer entry object without the layer being added to the workspace locale first.

[dbauszus-glx]

The vector_layer / layer entry method must support a reload method which will request the data from the query.

[simon-leech]

When you create an infoj type vector_layer, you have to provide a params.fields array, even if it's empty, or you get a crash that 'layer.params.fields' is not iterable.