Survey : don't clear all form fields that may be hidden

[labkey-klum]

Rationale

We are currently clearing all hidden form elements in a survey panel. I don't remember the exact reason for this behavior but I can imagine with some skip logic where we hide/show elements we don't want those values posted, although I thought ExtJS forms prevented that automatically although maybe this is just for disabled elements.

This came up recently while trying to help a client where they needed a value posted without rendering a visible element in the form. The exact scenario is there is a value that needs to be dynamically calculated based on other behavior, so a listener is attached and the value of the hidden form field is updated on parent element changes.