Progress: work on user pages

Progress: work on user pages

This makes the PATH_SELF constant for c_standard_path public.
Add new user session handling class.
Add a generic user-specific version of the c_standard_path and have most user path classes extend it.
Populate a basic version of the content menu for user paths.
User paths should accept user ids, handle the arguments.
The print, pdf, and ps paths are also in the url arguments as well as in a separate class path (I need to review the possibilities and pick only 1 method).
Just about all of the user paths, in their current form, are stubs and need to be implemented.