Optimize writing of synonyms config to Solr managed resource

[opensemanticsearch]

For performance issues with bigger thesauri, the synonyms config has to be written for the ontology/skos thesaurus at once, not for each concept.

[Mandalka]

Writing of synonyms to Solr managed resource API now all at once, so Solr has not to rewrite whole .json synonym config for each synonym.