Add support for OGC WFS/WFST 2.0

**Working on WFS 2.0 integration in openlayers**

This PR adds support for OpenGIS WFS 2.0. Interface Standard

  * Provide new OpenLayers.Format.WFST.v2_0_0
  * Provide new OpenLayers.Protocol..WFS.v2_0_0
  * Add test suite for this format

Specifications :
http://portal.opengeospatial.org/files/?artifact_id=39967

Related PR - Filters Encoding 2.0 : #1069
Related PR - WFS 2.0 capabilities Format : #1058