Policy Plus - Category tree construction

Some time ago, I finished writing the ADMX/ADML parsers for Policy Plus. The next thing to do is turn that data into useful hierarchies of objects (like the categories with parent/child relationships). So today, I started filling out the BuildStructures method with category management code. It can now figure out the tree structure of categories after loading. I also corrected the type of the ClientExtension field - it's supposed to be a GUID (or String), not a Boolean.

While testing the new code, I discovered something interesting about the default Windows ADMX files. Several categories defined in inetres.admx have invalid parents. That is, the parent field references a nonexistent category. The real Group Policy Editor seems to make these "orphaned" categories top-level categories when they try to reference categories in other ADMX files, but ignores them when they reference absent categories without a namespace prefix. Policy Plus's current behavior is to always put orphaned categories at the top level, but this will probably change eventually.