* Foundations of the XDMF mesh and file types.

* Setup of tests

* Working on reading XDMF

* Geometry processing complete

* Fixed crazy pointer issue with function by changing to subroutine

* Working up through vertices.

* Working up through vertices.

* Material import working

* Everything but mixed topo working for two pins test

* Prior to recursive assignment mods

* Working for multilevel grid after change to assignment

* Added mixed topology, just need to comment everything.

* Commented all import code and tests

* Whitespace

* Working on export. Also fixed CMake for HDF5 dependance

* XDMF export working up through leaves

* Working on writing leaves

* Working on geometry. Allocatable issue resolved

* Export working for single topology. Changed xdmf to UTF8 encoding.

* Mixed topology working

* Material ID export working

* All import export working. Need to implement tests.

* Added newline handling to xdmf

* Testing finished.

* Added distanceToLeaf function

* Added bounding box to XDMFMeshType

* Addressed thfolk suggestions, changed DBC to error handling

* Clear cell sets name with mesh%clear

* Clear boundingBox

* Addressed yl5 changes other than xml privacy

* Addressed yl5's comments

* Made children private

* Rewrote unit tests, renamed module, and removed file type

* Removed whitespace and a few blank lines.