Progress: further work on user view page, documentation changes, more global constant...

Progress: further work on user view page, documentation changes, more global constants, try to get more consistent return types

One of the downsides of my design is the complex return type handling.
The code because easier when tests do not have to be performed.

I want to provide a way to return a class as a default but provide a way to say that there was no value stored.
Instead of returning the NULL return type class, return the preferred class with an error flag set to "not defined".

This simplifies the code, especially some of the code used on the user view page.