adds a new empty field to the collection
|text||string||the text (value) for the new section (field)|
|string| number||the ID of a newly added field|
The method is applied to the collection, the new field will be added to the end.
All multitext fields have unique IDs that are generated by the component. The method will return the ID of the new field (afterwards the ID may be used for programmatically removing of the field with the removeSection method).