Add support for variable domains

[ondrej33]

In this pull request, we add support for directly restricting quantified variables' domains in HCTL formulae. These variable domains behave the same way as wild-card propositions introduced in #9, and they are evaluated to an arbitrary (coloured) set given by the user. The syntax is following: !{x} in %domain%:, and the same goes for other quantifiers. This way, the user can directly restrict the domain of every {x} encountered during bottom-up computation (makes the formula more readable and speeds up the computation).

The following equivalences hold:

• !{x} in %A%: phi = !{x}: %A% & phi
• 3{x} in %A%: @{x}: phi = 3{x}: @{x}: %A% & phi
• V{x} in %A%: @{x}: phi = V{x}: @{x}: %A% => phi

These changes are now also available as part of the tool itself, not just the library. The model checker can now load an archive with BDDs to be substituted for the wild-card properties and variable domains. It can also generate an archive with resulting BDDs.

Furthermore, this PR includes some refactoring, mainly related to syntax trees and the test suite.

[codecov]

Codecov Report

Attention: 63 lines in your changes are missing coverage. Please review.

Comparison is base (941bc1a) 89.39% compared to head (d9fb9f4) 87.18%.

Files	Patch %	Lines
src/generate_output.rs	0.00%	15 Missing ⚠️
src/load_inputs.rs	0.00%	15 Missing ⚠️
src/analysis.rs	65.51%	10 Missing ⚠️
src/evaluation/algorithm.rs	92.30%	6 Missing ⚠️
src/evaluation/eval_context.rs	66.66%	5 Missing ⚠️
src/preprocessing/tokenizer.rs	87.50%	5 Missing ⚠️
src/preprocessing/hctl_tree.rs	91.89%	3 Missing ⚠️
src/preprocessing/utils.rs	95.34%	2 Missing ⚠️
src/evaluation/mark_duplicates.rs	97.14%	1 Missing ⚠️
src/preprocessing/operator_enums.rs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #17      +/-   ##
==========================================
- Coverage   89.39%   87.18%   -2.22%     
==========================================
  Files          24       26       +2     
  Lines         792      944     +152     
==========================================
+ Hits          708      823     +115     
- Misses         84      121      +37     

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