Optional zIndex for fill symbolizers
Optional zIndex for stroke symbolizers
Optional zIndex for icon symbolizers
Optional zIndex for shape symbolizers
Optional zIndex for text symbolizers
Default value for zIndex
Removed unused stroke defaults for select intent
Merge pull request #1090 from tschaub/symbolizer-z

Add zIndex property to symbolizers.  Symbolizers with the same zIndex (in addition to other properties) are considered equal.  A subsequent change will sort features by symbolizer zIndex before rendering.