Before both initial SOC and final SOC were set to be zero, which
prevents synthetic fuel transfer over the year boundary, and prevents
the use of fossil fuels for non-zero CO2 scenarios.
Now done properly with cyclic Store (prevents accumulation of fossil
fuels as a form of sequestration) and Generator (to imitate fossil
fuel extraction).
tech name must only appear, but not be identical to generator
carrier. This allows to use the name "offshore" for both "offshore-ac"
and "offshore-dc", but then "solar" also catches "solar thermal",
which is fine since for solar thermal potentials are np.inf, unless
limit is 0 since np.inf*0 is nan.
Remove non-renewable generator and storage units from electricity-only
base network, since they're added differently here with links.
Remove unncessary cruft from config.yaml which is not used by
PyPSA-Eur-Sec (e.g. renewable configuration parameters).
Rename "naptha" to correct "naphtha".
