[FEATURE] asymmetric implementation of generic_branch

[petersalemink95]

For the discussions about generic_branch see #729.

The asymmetric implementation is more difficult and needs more thinking. Some options could be:

• Provide r1, x1, b1, g1, r2, x2, b2, g2 for positive and negative sequence and y_ff, y_ft, y_tf, y_tt for zero sequence
• Provide r_series / x_series and g/b_shunt_from/to
• Provide r1, x1, b1, g1, r2, x2, b2, g2, r0, x0, b0, g0, so provide the PI model for all sequences: this way only YnYn transformers can be calculated in asym calculation
• Derive other components from GenericBranch for the asymmetric calculation, like GenericBranchLine, GenericBranchTransYNyn, etc. With many generic implementations, it is not so generic anymore.