Add example for loading features via ProtocolProxy

[chrismayer]

Added another example to show how to use a GeoExt.data.proxy.Protocol to
load features into a FeatureStore and sync this store with a vector-layer.

[marcjansen]

Thanks for this. I have three very minor and cosmetic remarks:

1. Can you use the following as the background of the attribution control? I personally like this better, Your mileage may vary.

   diff --git a/examples/grid/feature-grid-w-proxy.html b/examples/grid/feature-grid-w-proxy.html
   index 044e23e..64bba6f 100644
   --- a/examples/grid/feature-grid-w-proxy.html
   +++ b/examples/grid/feature-grid-w-proxy.html
   @@ -14,7 +14,8 @@
   
               <style>
                   div.olControlAttribution {
   -                           background-color: #157FCC;
   +                           background-color: rgb(237,237,237);
   +                           background-color: rgba(237,237,237,0.7);
                       }
               </style>

2. Can we have a more distinct selected style of the features in the map? Sth. like:

   diff --git a/examples/grid/feature-grid-w-proxy.js b/examples/grid/feature-grid-w-proxy.js
   index 9a6b420..a4b1b49 100644
   --- a/examples/grid/feature-grid-w-proxy.js
   +++ b/examples/grid/feature-grid-w-proxy.js
   @@ -55,10 +55,22 @@ Ext.application({
            strokeColor: "yellow",
            graphicName: "circle"
        };
   -        var style = new OpenLayers.Style(template);
   +        var defStyle = new OpenLayers.Style(template);
   +        var selStyle = new OpenLayers.Style(
   +                Ext.apply(
   +                    Ext.apply({}, template),
   +                    {
   +                        strokeWidth: 3,
   +                        pointRadius: 15,
   +                        fontSize: "15px",
   +                        fontWeight: "bold"
   +                    }
   +                )
   +            );
        var vecLayer = new OpenLayers.Layer.Vector("vector", {
            styleMap: new OpenLayers.StyleMap({
   -                'default': style
   +                'default': defStyle,
   +                select: selStyle
            })
        });

3. You are mixing tabs and spaces in both html and js. Would you mind changing this to be all spaces?

This is a long comment, but everything is absolutely minor.

Please merge with or without adressing my remarks.

[chrismayer]

Thanks for the review @marcjansen, I adressed your comments and added two more commits.

[marcjansen]

Great & thanks, please merge!