Fix for issue #206 Global OL defaultSymbolizer assignment in WMSStylesDialog creates conflicts

Although issue #206 has been closed, I would like you to reconsider, also taken into the account the fix in the commits (the second is to undo a change in WFSProtocolProxy that went in by accident).

As I see it:

- the original code changes a global var: OpenLayers.Renderer.defaultSymbolizer. This affects not only OLEditor but any other component that uses the defaultSymbolizer
- by changing the name into OpenLayers.Renderer.defaultSymbolizerGXP (see commit) and using it in all assignments for defaults in GXP, IMO the SLD defaults are respected