removed all fox xml files
added fox as a submodule
configured new fox xml submodule for openmc
separated out git commands into two execute processes
now use fox cmakelists
fox now included as a subdirectory with its own CMakeLists
check for fox xml submodule before trying to initialize it
added documentation on working with FoX submodule
Merge branch 'develop' into fox_submodule

Conflicts:
	src/CMakeLists.txt
Removed glob for FoX source files.
Fix spacing in xml-parsing.rst.
Merge pull request #267 from mit-crpg/fox_submodule

Include FoX as git submodule