GitLab

ENH: Added XdmfGridUnstructured and turned XdmfGrid into an abstract base class for all grids (both structured and unstructured).  Modified a bunch of utils and other classes
to fit this new hierarchy.

ENH: Change some method names in XdmfArray to be clearer and less verbose.  Modify files for documentation clarity.  Modify some minor things to prevent -Wall warnings in gcc.  Add python install rules and rpathing.

ENH: Clean up XInclude additions.  Verify that writing reading and writing an XPath/XInclude file produces the same file.

ENH: Add XPath writing capabilities to XdmfWriter.  Whenever a duplicate XdmfItem is written to disk, instead of writing it twice, XPath the first.  We will hopefully mirror this behavior when reading in.