Add support for the extremely awesomely super-comprehensive rule based styling

that Andreas has been working so hard on. I think this is the single most
awesome commit I've ever had the pleasure of committing. The results of this
commit are described on http://trac.openlayers.org/wiki/Styles: essentially,
this makes it possible to style features in all kinds of fun ways based on
rules, and will also form the underlying basis for #533. Things this patch
adds:

 * OL.Rule classes. These classes allow you to do tests against the propertie
   of a feature, and set a style based on these properties -- so you can
   compare the 'speedlimit' property of a line, and test if it is > 60, and if
   it is greater than 60, render it in a different color. You can also test
   combinations of rules using the OL.Rule.Logical class, and test featureids
   with the FeatureID class. 
 * OL.Style class: The OL.Style class lets you wrap up Rules into styles that 
   can be used with drawFeature to draw the feature in the selected style.
 * OL.Layer.Vector.drawFeature will check if the given style is an OL.Style
   object, and if so, it will draw the feature accordingly.

examples/georss-flickr.html shows usage of these classes.

Many, many thanks go to Andreas for all his hard work on this: this code really
is very pretty, and includes unit tests for all the classes (and we know that I
am a big fan of tests.)

Three cheers for Andreas: Hip hip, hooray! hip hip, hooray! hip hip, hooray!


git-svn-id: http://svn.openlayers.org/trunk/openlayers@5429 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Layer/Vector.js

@@ -350,6 +350,12 @@ OpenLayers.Layer.Vector = OpenLayers.Class(OpenLayers.Layer, {
                 style = this.style;
             }
         }
+
+        if (style && style.CLASS_NAME && 
+            style.CLASS_NAME == "OpenLayers.Style") {
+            style = style.createStyle(feature);
+        }    
+        
         this.renderer.drawFeature(feature, style);
     },