Emphasize attribute units for standard lines types

[sebastian-peter]

Don't know what the best solution would be, but somehow, I think, we should mention in the standard line type section what units the columns have. I think not everybody will make the connection to the type table at the top.

Specifically, it should be more obvious that b, g, r, x are specified as Ohm/km and µS / km.

Same thing applies to standard transfomers, although less urgent