UPD: Decomposition of node-connecting components, addition of quadratic formulations

[tasseff]

Closes #106, closes #101, closes #98, closes #92, closes #89, closes #75, closes #28.

[codecov]

Codecov Report

Merging #111 into master will decrease coverage by 6.02%.
The diff coverage is 84.08%.

@@            Coverage Diff             @@
##           master     #111      +/-   ##
==========================================
- Coverage   86.18%   80.15%   -6.03%     
==========================================
  Files          24       27       +3     
  Lines        2294     2207      -87     
==========================================
- Hits         1977     1769     -208     
- Misses        317      438     +121     

Impacted Files	Coverage Δ
src/WaterModels.jl	100.00% <ø> (ø)
src/util/compute_cuts.jl	0.00% <0.00%> (ø)
src/util/unbinarize.jl	0.00% <0.00%> (ø)
src/prob/des.jl	66.66% <58.62%> (-8.34%)	⬇️
src/util/obbt.jl	79.55% <70.65%> (-12.12%)	⬇️
src/core/data.jl	59.50% <80.95%> (+11.36%)	⬆️
src/core/ref.jl	87.31% <81.08%> (-4.56%)	⬇️
src/io/epanet.jl	71.00% <81.39%> (-2.35%)	⬇️
src/form/directed_flow.jl	89.15% <85.00%> (-7.32%)	⬇️
src/core/constraint_template.jl	80.24% <90.65%> (-14.89%)	⬇️
... and 34 more

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