use SMW ExporterFactory & Cache

[thomas-topway-it]

This PR is made in reference to: #116

• (JsonLDSerializer) uses directly SMW ExporterFactory instead of ExportRDF special page's url
• decouples error log (SMW RDFXMLSerializer from EasyRdf)
• uses Cache as introduced here Harden JSON-LD RDF fetch path with error handling #118

This PR includes:

• Tests (unit/integration)
• CI build passed

[codecov]

Codecov Report

❌ Patch coverage is 0% with 27 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.44%. Comparing base (d455dfa) to head (eaba33b).

Files with missing lines	Patch %	Lines
src/JsonLDSerializer.php	0.00%	27 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #120      +/-   ##
============================================
- Coverage     77.88%   75.44%   -2.44%     
  Complexity       81       81              
============================================
  Files             8        8              
  Lines           217      224       +7     
============================================
  Hits            169      169              
- Misses           48       55       +7     

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[thomas-topway-it]

@gesinn-it-gea there is a test error which seems unrelated to the edits