Adding first working version of the DualMesher filter

This version contains a preliminar implementation of the dual mesher, ImageData reader and Mesh writer. Some details have to be checked but the filter is connected and operational. 
For the moment we have included a dependency to the ITK Kitware library for the image operations. All dependencies with VTK have been eliminated.
We have also used the Xercesc library to read the Metadata.xml files used for the parameters of each filter.