OpenLayers.Layer.WFS


******* TO BE COMPLETED ***********

This class gives the possibility to add a WFS layer to an OpenLayers map as a vector layer.
Features are retrieved from the server, gml is parsed to create OpenLayers.Feature.
Then, updated, inserted and deleted features can be transactionnaly commited to the server back.

* Constructor
  OpenLayers.Layer.WFS(name, url, params, options) -- URL is the base URL to the layer. Params is a set of params to be included in the HTTP Request. Options is a set of options, extending the parameters of the layer.

* Methods
  destroy() -- none -- 
  setMap(map) -- none -- Set the map property of the layer. Also set the parameters which are inherited from the map. This is also where the tileSize is retrieved from the map. Subclassed from {OpenLayers.Layer}.
  onMapResize() -- none -- inherited from OpenLayers.Layer.Vector
  moveTo({OpenLayers.Bounds|bounds}, {Boolean|zoomChanged}, {Boolean|dragging}) -- none -- inherited from OpenLayer.Layer.Vector
  addFeatures({Array of {OpenLayers.Feature}|features}) -- {Array} -- inherited from OpenLayer.Layer.Vector
  removeFeatures({Array of {OpenLayers.Feature}|features}) -- {Array} -- inherited from OpenLayer.Layer.Vector
  updateFeatures({Array of {OpenLayers.Feature}|features}) -- none -- inherited from OpenLayer.Layer.Vector
  commit() -- none -- inherited from OpenLayers.Layer.Vector
  refresh() -- none -- redraws the layer, i.e. clears the features array, relaunch a WFS request and redraws features on the map
  
  getURL({OpenLayers.Bounds|bounds}) -- {String} -- Returns a WMS URL for the given bounds based on the properties of the layer.
  All other methods are inherited from {OpenLayers.Layer.Grid}
  
* Options 
  geometry_column -- {string} -- set the name of the field used for geometry, needed for commits
  geometryType -- {Object} -- defines the geometry type allowed for the layer, if not set or null, no constraint is available
  style -- {OpenLayers.Style} -- Set the style to use to render geometries on the renderer
  
* Params
  Available params are defined by the WFS service, here are some examples : typename, maxfeatures, maxZoomLevel, propertyname