OL renderer for vectorial layers.

The vector layers are very important in OL, much of the code is devoted to this.

At the request [Custom-strategy-using-heatmap](http://osgeo-org.1560.n6.nabble.com/Custom-strategy-using-heatmap-td5042456.html) of @Polzme I proposed a renderer for vector layers (seems to be the intention of using this renderer in OL-Drupal module see: [heatmaps-vector-layer](http://openlayers-dev.nid-de-poule.be/example/24/heatmaps-vector-layer))

This renderer also solves two issues of Hadmap layer:
  * prevents the attenuation in areas near the edges of map
  * resize map