ZF-6830: Allow editing/updating of options for decorators already in a zend_form_elements stack.
Sometimes its particularly useful to be able to change options of individual decorators out of an elements decorator stack without having to re-set the entire thing manually (ie when using a preset list of elements and customising minor aspects for the current output). At the moment the closest thing to this would be to use removeDecorator and then addDecorator with the new options list. (which only works for the item on the end of the stack, not the most useful since the order of the stack is important in this case)
something like $element -> setDecoratorOption($decoratoridentifier, $option) and $element -> removeDecoratorOption($decoratoridentifier, $option)
of course the tricky bit i can see here is that decorators dont really get names, at best they're identifiable by their type and the order of that type in the stack. (ie if the stack was viewhelper,htmltag,label,htmltag to ident the htmltags would be htmltag:0, htmltag:1 etc. not ideal since you cant always guarantee the order of the stack if something else is setting it.)