This is easy to miss and causes confusing behavior
(e.g. wrong page/option selected)

We were actually crashing for visible parameters without 'gui-text'
otherwise.

Also make sure we actually *do* bail out if we have parameters
missing required fields and throw/catch an exception instead of
producing broken instances.

let's hope this works as expected...

For this take a first step towards properly tracking children
of each parameter and provide functions to look up all widgets.

Also rename overloaded string() functions, so it's clear what they
actually do, as it's not the same thing at all...