Provide an N-Triple editor

[fsteeg]

When working with Metafacture, our target format is usually RDF serialized as N-Triples. When working in the Metafacture IDE, we have editors with syntax coloring and syntax checking for all files involved (input XML, morph.xml, Flux, DOT) except the output files. So an Xtext-based N-Triple editor would complete the editor support.