Composite correlation models

[longemen3000]

This adds initial support for "Composite correlation models" what is this? basically a model that holds liquid, gas and saturation models. it is useful in assisting other models, like activity models. the end goal would be to make γ-ϕ equilibria.
it also introduces some auxiliary EoSModels (SaturationModel, LiquidVolumeModel) that will be required for #117 (specially LiquidVolumeModel)
What is missing:

• some interfaces
• tests (the tests will be integrated on Activity equilibria methods rework, chapman activity coefficient #119, ideally, a γ-ϕ eq with correlations should be possible.

[codecov-commenter]

Codecov Report

Base: 83.55% // Head: 81.12% // Decreases project coverage by -2.43% ⚠️

Coverage data is based on head (49cdc67) compared to base (47d3e06).
Patch coverage: 25.38% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #118      +/-   ##
==========================================
- Coverage   83.55%   81.12%   -2.44%     
==========================================
  Files         184      196      +12     
  Lines       11782    12177     +395     
==========================================
+ Hits         9845     9879      +34     
- Misses       1937     2298     +361     

Impacted Files	Coverage Δ
src/database/ParamOptions.jl	100.00% <ø> (ø)
src/database/params/AssocParam.jl	36.92% <0.00%> (-21.62%)	⬇️
src/methods/property_solvers/volume.jl	93.47% <ø> (-0.08%)	⬇️
src/models/CompositeModel/CompositeModel.jl	0.00% <0.00%> (ø)
...ompositeModel/LiquidVolumeModel/COSTALD/costald.jl	0.00% <0.00%> (ø)
...LiquidVolumeModel/DIPPR105Liquid/DIPPR105Liquid.jl	0.00% <0.00%> (ø)
...teModel/LiquidVolumeModel/Rackett/RackettLiquid.jl	0.00% <0.00%> (ø)
src/models/Virial/AbbottVirial/AbbottVirial.jl	0.00% <0.00%> (ø)
src/models/Virial/EoSVirial/EoSVirial.jl	0.00% <0.00%> (ø)
...dels/Virial/TsonopoulosVirial/TsonopoulosVirial.jl	0.00% <0.00%> (ø)
... and 25 more

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