Update documentation

[jardinetsouffleton]

This MR adds documentation to the entire codebase.

[codecov]

Codecov Report

Merging #301 (5429f9c) into master (f1806b8) will decrease coverage by 0.03%.
The diff coverage is 100.00%.

❗ Current head 5429f9c differs from pull request most recent head 5b1ffb0. Consider uploading reports for the commit 5b1ffb0 to get more accurate results

@@            Coverage Diff             @@
##           master     #301      +/-   ##
==========================================
- Coverage   67.87%   67.83%   -0.04%     
==========================================
  Files         136      136              
  Lines        5883     5883              
==========================================
- Hits         3993     3991       -2     
- Misses       1890     1892       +2     

Impacted Files	Coverage Δ
src/CP/constraints/absolute.jl	81.96% <ø> (ø)
src/CP/constraints/alldifferent.jl	94.18% <ø> (ø)
src/CP/constraints/binaryequivalence.jl	80.95% <ø> (ø)
src/CP/constraints/binaryimplication.jl	76.66% <ø> (ø)
src/CP/constraints/binarymaximum.jl	81.57% <ø> (ø)
src/CP/constraints/binaryor.jl	80.00% <ø> (ø)
src/CP/constraints/binaryxor.jl	80.95% <ø> (ø)
src/CP/constraints/compacttable.jl	89.47% <ø> (ø)
src/CP/constraints/disjunctive.jl	95.86% <ø> (ø)
src/CP/constraints/element2d.jl	90.12% <ø> (ø)
... and 14 more

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