Text field converter refactoring

> Hi all,
>  
> I've refactored the ObjectStringConverter support to be more flexible and provide
> feedback in the UI (via corner triangle).
>  
> Also, should be no more MNU's in, for example, ColorSelectorDialogWindow when
> numeric fields are made empty!
>  
> Note that any fields in use need to be recreated.
> A save of the image (or otherwise) is required to reinitialize the EditorFindReplaceDialogWindow singleton.
>  
> Attached cs.
>
> Regards, Gary
> <TextFieldRegex.3.cs>