Update biogas potentials for new scenarios

[ClaraBuettner]

Limited biogas potential has to be adjusted for the scenario path. It should consider unsustainable biogas (for the years where it is available) and sustainable biogas.

Needs to be adjusted here:

eTraGo/etrago/tools/constraints.py

Lines 1684 to 1687 in a6a3005

	"eGon100RE": {
	"biogas": 14450103
	}, # [MWh] Value from reference p-e-s run used in eGon-data
	}

[ClaraBuettner]

New results from pypsa-eur run:
In Germany, 133465841.78 MWh of biogas have been feed into the gas grid for the year 2045:
(calculated by network.links_t.p0[network.links[network.links.index.str.startswith("DE0 0 biogas to gas")].index].sum().sum()*3)

[ClaraBuettner]

For all countries, the usage looks like this:

AL0 0 biogas 3.161167e+05
AT0 0 biogas 1.906582e+07
BA0 0 biogas 4.011812e+06
BE0 0 biogas 3.990887e+07
BG0 0 biogas 1.099119e+07
CH0 0 biogas 7.093149e+06
CZ0 0 biogas 2.473895e+07
DE0 0 biogas 1.334658e+08
DK0 0 biogas 2.631969e+06
DK1 0 biogas 9.344797e+05
EE0 0 biogas 1.525177e+06
ES0 0 biogas 6.300249e+07
ES2 0 biogas 1.654294e+06
FI1 0 biogas 1.265250e+07
FR0 0 biogas 8.509130e+07
FR6 0 biogas 1.434945e+05
GB3 0 biogas 2.596067e+07
GB4 0 biogas 7.000204e+05
GR0 0 biogas 1.118149e+07
HR0 0 biogas 2.556322e+06
HU0 0 biogas 1.796744e+07
IE4 0 biogas 1.105717e+07
IT0 0 biogas 5.975349e+07
IT5 0 biogas 1.954873e+06
LT0 0 biogas 6.741336e+06
LU0 0 biogas 1.911178e+06
LV0 0 biogas 1.944465e+05
ME0 0 biogas 3.063449e+05
MK0 0 biogas 6.616678e+05
NL0 0 biogas 6.079801e+07
NO1 0 biogas 1.061794e+08
PL0 0 biogas 6.196918e+07
PT0 0 biogas 9.156813e+06
RO0 0 biogas 2.308365e+07
RS0 0 biogas 3.940441e+06
SE1 0 biogas 8.794408e+06
SI0 0 biogas 3.804496e+06
SK0 0 biogas 1.351494e+07
XK0 0 biogas 4.075439e+05

I used this code to produce the list:
network = pypsa.Network(/path/to/pypsaeur/postnetwork/2045)
biogas_links = network.links[network.links.carrier=="biogas to gas"]
biogas_links["dispatch"] = network.links_t.p0[biogas_links.index].sum()*3
biogas_links.groupby(biogas_links.bus0).dispatch.sum()