Added zero cardinality constraint rules

[robert-david]

#316

Added counting for zero cardinality triple constraints.
Added node targeting based on shape map.

[codecov-commenter]

Codecov Report

Merging #317 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #317   +/-   ##
=======================================
  Coverage   46.91%   46.91%           
=======================================
  Files          52       52           
  Lines        1914     1914           
  Branches       62       62           
=======================================
  Hits          898      898           
  Misses       1016     1016           

Impacted Files	Coverage Δ
...ng/src/main/scala/es/weso/slang/SLang2Clingo.scala	82.05% <ø> (ø)

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[labra]

Thanks for the PR.

It would be great to configure the system to have some tests for the Clingo encoding, but at this moment we don't have it yet, so I merged it anyway.