Adding new classes vtkXMLUniformGridAMRDataWriter /
vtkXMLPUniformGridAMRDataWriter based on vtkXMLHierarchicalBoxDataWriter /
vtkXMLPHierarchicalBoxDataWriter to write all types of AMR datasets in VTK XML
format. vtkXMLHierarchicalBoxDataWriter and vtkXMLPHierarchicalBoxDataWriter are
now simply empty subclasses for backwards compatibility.

The XML file format had to be extended to write enough meta-data to support
loading of Overlapping AMR datasets correctly. Consequently, the version number
was updated to 1.1.

Adding vtkXMLUniformGridAMRReader for reading VTK XML files for AMR datasets
(overlapping and nonoverlapping). Also added a new test TestAMRXMLIO.
vtkXMLUniformGridAMRReader reader v1.1. For older versions, added a converter
vtkXMLHierarchicalBoxDataFileConverter (and a test) that converts the xml to the
new format. vtkXMLUniformGridAMRReader provides appropriate meta-data in
RequestInformation() pass, similar to other AMR reader such as Flash/Enzo.

vtkXMLGenericDataObjectReader has been updated to use
vtkXMLUniformGridAMRReader for reading all types of AMR datasets.

Change-Id: I3f143c266562f039a57a745835728c5750c8e463