[FTheoryTools] Overhaul Serialization

[HereAround]

• Use existing dict serialization for FTheory models.
• Clean up serialization code.
• Extend serialization of FTheory models to more of their associated data - anything that is currently stored as string, list of strings or boolean values is remembered by the serialization, once this PR is merged.

[I initially hoped to push this so that some of the JSON-files - that currently specify models - can be replaced by their mardi counterparts. This is not possible. Some of the data associated to the models cannot yet be serialized. For instance Lie algebras. I have not checked if there are other data types that we use and lack serialization (for instance graphs, as used for the QSMs. So I postpone this for now.]

cc @antonydellavecchia @apturner @emikelsons

[codecov]

Codecov Report

Attention: Patch coverage is 98.46154% with 2 lines in your changes missing coverage. Please review.

Project coverage is 84.08%. Comparing base (a8d2911) to head (6315982).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3932   +/-   ##
=======================================
  Coverage   84.07%   84.08%           
=======================================
  Files         592      592           
  Lines       81758    81722   -36     
=======================================
- Hits        68739    68713   -26     
+ Misses      13019    13009   -10     

Files	Coverage Δ
...eoryTools/src/Serialization/hypersurface_models.jl	100.00% <100.00%> (ø)
experimental/FTheoryTools/src/types.jl	95.00% <100.00%> (+0.88%)	⬆️
...erimental/FTheoryTools/test/hypersurface_models.jl	100.00% <100.00%> (ø)
experimental/FTheoryTools/test/tate_models.jl	100.00% <100.00%> (ø)
...perimental/FTheoryTools/test/weierstrass_models.jl	100.00% <100.00%> (ø)
...ntal/FTheoryTools/src/Serialization/tate_models.jl	97.43% <95.65%> (+5.22%)	⬆️
...heoryTools/src/Serialization/weierstrass_models.jl	97.43% <96.00%> (+5.22%)	⬆️

[emikelsons]

Looks good to me and all of the tests passed.

[HereAround]

Looks good to me and all of the tests passed.

Then I let @antonydellavecchia make the final call. Would like to know if this is ok/acceptable as long as the OSCAR serialization standards are concerned. @antonydellavecchia, if/once you are happy, please consider merging.