Add series branch flow

[rodrigomha]

I'm installing PSSE to validate the test case 26 line flows.

[github-actions[bot]]

Performance Results	Version	Precompile Time
Master	8.434344714
This Branch	8.387679045

Version	Execute Time
Master-Build ResidualModel	11.385581877
Master-Execute ResidualModel	53.143156404
Master-Build MassMatrixModel	1.130960988
Master-Execute MassMatrixModel	52.557780974
This Branch-Build ResidualModel	12.202900695
This Branch-Execute ResidualModel	54.618148168
This Branch-Build MassMatrixModel	1.141749491
This Branch-Execute MassMatrixModel	55.4389261

ResidualModel and MassMatrixModel performance results should be compared between versions and not between models due to the execution order of the tests

[codecov[bot]]

Codecov Report

Merging #264 (96966ea) into master (828043d) will increase coverage by 0.03%. The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master     #264      +/-   ##
==========================================
+ Coverage   90.81%   90.84%   +0.03%     
==========================================
  Files          65       65              
  Lines        7019     6958      -61     
==========================================
- Hits         6374     6321      -53     
+ Misses        645      637       -8     

Flag	Coverage Δ
unittests	90.84% <80.00%> (+0.03%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/base/simulation_results.jl	69.89% <80.00%> (+4.99%)	:arrow_up:
src/base/simulation_model.jl	0.00% <0.00%> (-100.00%)	:arrow_down:
src/base/small_signal.jl	80.80% <0.00%> (-1.60%)	:arrow_down:
src/base/device_wrapper.jl	85.00% <0.00%> (-0.37%)	:arrow_down:
src/base/simulation_initialization.jl	84.07% <0.00%> (-0.23%)	:arrow_down:
src/models/device.jl	94.35% <0.00%> (-0.22%)	:arrow_down:
src/base/jacobian.jl	95.58% <0.00%> (-0.19%)	:arrow_down:
src/base/perturbations.jl	58.42% <0.00%> (-0.15%)	:arrow_down:
src/base/simulation.jl	89.55% <0.00%> (-0.06%)	:arrow_down:
src/initialization/init_device.jl	96.38% <0.00%> (-0.03%)	:arrow_down:
... and 13 more