Refactoring elements into more manageable groups

Broken the table of elements into groupings.

ToDo: Change Elements.md to point to the new locations
Updated elements.md with summary & pointer.

Removed the list of elements from elements.md. Added a description of
the new elemental breakdown, and invited contribution.
Updated Contribute.md

Updated section on how to update to elements, and how to format.

TODO: Add links to files on GitHub.
Added links to element groups.
Added link to Infrastructure element group.
Added new refactoring ToDo.
Merge pull request #3 from camassey/master

Refactored the elements, updated docs