Feature/fix rdfa parser

[MaillPierre]

Adds the RDFa parser as based on the RDFa-core recommendation https://www.w3.org/TR/rdfa-core/

[github-actions]

Overall Project	50.26% -0.41%	🍏
Files changed	62.57%	🍏

File	Coverage
RDFaInitialPrefixes.java	100%	🍏
RDFaAttributes.java	100%	🍏
RDFFormat.java	99.34%	🍏
RDFa.java	97.01% -2.99%	🍏
SerializerFactory.java	87.35%	🍏
ParserFactory.java	66.25% -1.88%	❌
AbstractGraphSerializer.java	63.32%	🍏
PrefixHandler.java	61.32%	🍏
RDFaEvaluationContext.java	56.62% -43.38%	❌
RDFaParser.java	54.68% -43.04%	❌
RDFaProcessingContext.java	45.65% -54.35%	❌
AbstractNamespace.java	32.69%	🍏
RDFaIncompleteStatement.java	0% -4.4%	❌

[github-actions]

Test Results

997 tests  +4   997 ✅ +4   36s ⏱️ +3s
 72 suites ±0     0 💤 ±0 
 72 files   ±0     0 ❌ ±0 

Results for commit 89a5521. ± Comparison against base commit 0cd4a9f.

[github-actions]

Overall Project	50.28% -0.39%	🍏
Files changed	63.82%	🍏

File	Coverage
RDFaInitialPrefixes.java	100%	🍏
RDFaAttributes.java	100%	🍏
ModelNamespace.java	100%	🍏
RDFFormat.java	99.34%	🍏
RDFa.java	97.01% -2.99%	🍏
SerializerFactory.java	87.35%	🍏
ParserFactory.java	66.25% -1.88%	❌
AbstractGraphSerializer.java	63.32%	🍏
PrefixHandler.java	61.32% -2.14%	❌
RDFaProcessingContext.java	57.91% -42.09%	❌
AbstractModel.java	57.41%	🍏
RDFaEvaluationContext.java	56.62% -43.38%	❌
RDFaParser.java	55.45% -42.29%	❌
AbstractNamespace.java	32.69% -26.92%	❌
RDFaIncompleteStatement.java	0% -15.96%	❌