Harmonise year for weather and year for energy totals

[nworbmot]

Currently the weather year (default 2013) in PyPSA-Eur is different from the year used for energy totals in build_energy_totals.py (fixed to 2011). The total energy for heating is used for rescaling the heat load profiles, so this should be the same year.

[martavp]

Industry data corresponds to the year 2015. If needed, it can be easily adapted to a previous year.

[fneum]

This is done via #621 #204