db_xml.py: put(): Raise an error if there are multiple fields with the same name, instead of silently overwriting the first with the second. This generally indicates the need to use `:[@merge=1]` on the fields in question.
db_xml.py: put(): Raise an error if there are multiple fields with the same name, instead of silently overwriting the first with the second. This generally indicates the need to use `:[@merge=1]` on the fields in question.