Use oxrdf & oxrdfio instead of oxigraph

[hoijui]

-> Significantly smaller dependencies and shorter compile-time

[Tpt]

Thank you! If you want to simplify the code slightly, there is a way for parse_turtle to easily return a Graph(see inline comment)

An other option might be to use the oxttl::TurtleParser crate directly

[hoijui]

I now switched oxrdfio -> oxttl, and am not using Dataset anymore

[Tpt]

Thank you!