Better way of indicating width for linesymbolizer.

[Skywave]

To avoid duplicating rules for different zoomlevels, making it one simple way indicating multiple scaledemoniators. Example from osm.xml

2992 	  <Style name="roads">
2993 	    <!-- MOTORWAY-->
2994 	    <!-- level 4-5 -->
2995 	    <Rule>
2996 	      <Filter>[highway] = 'motorway' or [highway] = 'motorway_link'</Filter>
2997 	      <MaxScaleDenominator>25000000</MaxScaleDenominator>
2998 	      <MinScaleDenominator>5000000</MinScaleDenominator>
2999 	      <LineSymbolizer>
3000 	        <CssParameter name="stroke">#809bc0</CssParameter>
3001 	        <CssParameter name="stroke-width">1</CssParameter>
3002 	      </LineSymbolizer>
3003 	    </Rule>
3004 	    <!-- level 6-8 -->
3005 	    <Rule>
3006 	      <Filter>[highway] = 'motorway' or [highway] = 'motorway_link'</Filter>
3007 	      <MaxScaleDenominator>5000000</MaxScaleDenominator>
3008 	      <MinScaleDenominator>1000000</MinScaleDenominator>
3009 	      <LineSymbolizer>
3010 	       <CssParameter name="stroke">#809bc0</CssParameter>
3011 	       <CssParameter name="stroke-width">1.5</CssParameter>
3012 	      </LineSymbolizer>
3013 	    </Rule>
3014 	    <!-- level 9 -->
3015 	   <Rule>
3016 	     <Filter>[highway] = 'motorway' or [highway] = 'motorway_link'</Filter>
3017 	      <MaxScaleDenominator>1000000</MaxScaleDenominator>
3018 	      <MinScaleDenominator>500000</MinScaleDenominator>
3019 	      <LineSymbolizer>
3020 	      <CssParameter name="stroke">#809bc0</CssParameter>
3021 	      <CssParameter name="stroke-width">2</CssParameter>
3022 	    </LineSymbolizer>
3023 	   </Rule>
3024 	<Rule>
3025 	     <Filter>[highway] = 'motorway' or [highway] = 'motorway_link'</Filter>
3026 	      <MaxScaleDenominator>500000</MaxScaleDenominator>
3027 	      <MinScaleDenominator>200000</MinScaleDenominator>
3028 	      <LineSymbolizer>
3029 	      <CssParameter name="stroke">#809bc0</CssParameter>
3030 	      <CssParameter name="stroke-width">2.5</CssParameter>
3031 	    </LineSymbolizer>
3032 	   </Rule>

would become something like this.

<Filter>[highway] = 'motorway' or [highway] = 'motorway_link'</Filter>
<MaxScaleDenominator>25000000</MaxScaleDenominator>
<MinScaleDenominator>200000</MinScaleDenominator>
<LineSymbolizer>
<CssParameter name="stroke">#809bc0</CssParameter>
<CssParameter name="stroke-width-auto">25000000:1,5000000:1.5,1000000:2,500000:2.5</CssParameter>
</LineSymbolizer>