Fix updating variables during variable imports

[ephraimbuddy]

We should only create new variables during variable imports and not update already existing variables.

[potiuk]

I think we should a flag specifying that behaviour. I think the flag should be something of (probably too long name):

--action-on-existing-key: override (default) skip fail 

IMHO override shoudl remain as it is (default), as it could break existing usages.

[ephraimbuddy]

I think we should a flag specifying that behaviour. I think the flag should be something of (probably too long name):

--action-on-existing-key: override (default) skip fail 

IMHO override shoudl remain as it is (default), as it could break existing usages.

Implemented this also in the UI with radios:

I can't think of a better name than the one you suggested.