Fix missing documentation in XdmfIO.h.

Also, add XdmfIO.h to the *.pri file for proper inclusion in Qt Creator projects.
Update documentation to include C++11 functions (e.g., move-constructor).

Also, fix error in declaration within SLList class.
Fix error in file-extension/index determination function.
Debug XDMF-writing functions.

Runtime errors seem to be gone.  Valgrind errors are all within the Xdmf libraries and thus not under my easy control.

Generated file can be read-in by ParaView.  4D dataset causes errors since ParaView expects 3D or less.  Spacing and origin values within the XDMF XML file are for 3D, regardless of the shape of the actual data array.  Not sure that the values are correct for lower-dimensional data, though.
Change means of user-defining origin/spacing.
Implement XDMF output.

Compiles, not tested.
Update XDMF output.

Add ability to write a single grid of data without creating a hierarchal structure.  This helps visualization in ParaView by not creating a multi-block dataset.  This also simplifies the XDMF file by not creating a tree grid with a single child.
Merge branch 'master' into dev

Conflicts:
	src/Array4D.cpp
	src/XdmfIO.h
	test-xdmf/basicXdmfTest/basicXdmfTest.cpp
	test-xdmf/main.cpp