Remove unused GraphApi#total_demand_for_electricity_lole

This was a temporary method made redundant by the newer LOLE calculation
(using "demand_curve" with an argument).

Closes #671
ETSource "refresh" now performs a git-reset

Under no circumstances should a live server ever have a copy of a branch
which is different from the corresponding remote on GitHub. To prevent
(very rare) merge conflicts, we now do a git-fetch and git-reset to
ensure that branches always match those on GitHub.

Closes #561
Adapted comment to the removal of imported_steam_hot_water
Renamed buildings_final_demand_for_space_heating_heat. Fixes https://github.com/quintel/etsource/issues/730
Merge pull request #683 from quintel/rename_buildings_final_demand_for_space_heating_heat

Renamed buildings_final_demand_for_space_heating_heat.