JSON-LD exporting and reparsing results in different statements

When exporting triples as JSON-LD and using the JSON-LD parser to parse the result again, the resulting triples are different. The reason seems to be that plain literals when parsed again get the type "xsd:string". I am not sure if this is an issue in KiWi or in Sesame, we have to check this.

A test is in marmotta-core/LinkedDataTest - the JSON-LD tests have been ignored for this reason.