Proper handling of option changes for dependant fields

[timolemke]

Based on the workaround in 9997d73
If an options technical- or displayValue changes, the potential dependant field config of another formElement must be updated accordingly!

The problem:

• A dependant field might reference another field with options (e.g. RadioButtons). If so, it will be visible, if the referenced fields value matches exactly the value which was configured in the dependant field.
• If the options technical- or display-Value of the referenced field is changed by the editor, but the dependant field is not updated, the dependantField will never be shown in the frontend, because the required value cannot be selected by the user.