Need to add description comment header to XML files

Both the registry and various namelist definition files could benefit from having a commented header that describes what all of the various XML elements in the file represent, and thus when/how they should be used.

Along with that, all registry and namelist definition files (including those being used in testing) should have the same `version` value when compared to other files of the same kind, and should not contain any reference to an `xsl` file, as no files of that type currently exist in CAMDEN (and it is unclear if it is even needed at all).

Start by locating the registry and namelist definition XML files, including the versions used in testing, and compare their commented structure, version values, and xsl references. Done means each relevant file has a descriptive header, matching version values within its file kind, and no xsl reference.

Written by the indexing model from the issue text.