Support multiple symbolizers per rule in OpenLayers.Format.SLD and OpenLayers.Rule

[ahocevar]

OpenLayers.Rule does not represent one aspect of SLD: multiple symbolizers of the same type (Point, Line, Polygon, Text, ...) in a single rule. The symbolizer property can just hold one symbolizer of each type.

While rendering such rules is something that is planned for OpenLayers 3.0 ( http://trac.openlayers.org/wiki/three/MultipleSymbolizers), a structure representing it can be added now without much effort. This will be useful for applications that modify SLD for server-side (WMS) rendering.

The proposal is to add a Rule.symbolizers property with a structure like this:

rule.symbolizers = {
    "point": [pointSymbolizer1, pointSymbolizer2],
    "text": [textSymbolizer]

rule.symbolizer will not be affected by this change, and Format.SLD can write both properties when reading an SLD doc.

[crschmidt]

I don't think this is likely to be done in 2.8, or particularly neccesary. If someone is planning on working on it, we can pull it back. Otherwise, since I think Andreas mentioned this is not hard and he's going to need it, so I'm going to push it to 2.9 for now. Future is better if no one has immeddiate plans to implement.