Allow variable duplication within the same table

[ymarcon]

In order to facilitate the design of a data dictionary of longitudinal data in wide format, it would be good to have a button that allows to replicate a variable with a new name (VAR_1, VAR_2 etc.). This is not a process of derivation, this is a replication, whatever the variable belongs to a raw table or a view (in the case of a view, the script could be edited as well ?).

Reported by @ddoiron