[bulk] Some car updates

create alias cabriolet -> convertible
create implication convertible -> car

Link to request

Yes, a convertible can also be a tablet but I guess that is covered with the tablet-tag (and there are only cars under the convertible tag).
And a convertible is a "special" car^^.

We don't need an alias for cabriolet. It's meaning is ambiguous anyway since it can refer to a carriage.

@albert
I updated it. Should be fine now?

The bulk update request #528 has been approved.