Implementation of dynamic line rating for intermediate years

[ClaraBuettner]

For the intermediate year of our scenario path it is questionable which lines will get dynamic line rating first.
We could make use of the iterations of the lopf to find out which lines need to be extended first, assuming that they will be updated with dynamic line rating in the beginning.

As an easier alternative, we can select a year from which on dynamic line rating is available for all years.
This would require the implementation of an optional dynamic line rating within eTraGo.