Support turtle prefixes

[KasperZutterman]

Find out if it's possible to add prefixes in a Page, that can be used with the serializer.

Example: @prefix sosa: <http://www.w3.org/ns/sosa/> .

[KasperZutterman]

Look into https://github.com/rdfjs/N3.js/ instead of https://github.com/rubensworks/rdf-serialize.js

Basic-LDES-Server/src/lib/Page.ts

Line 32 in 6a15466

return rdfSerializer.serialize(tripleStream, {contentType: contentType});