owl2_from_rdf tidy-up

[cmungall]

• is there any need to include the utils file? not simpler to keep as one file, OR modularize
• change name of convert/3 to something more meaningful OR do not expose via export
• should we make some of the arguments Options members?

[vangelisv]

I used include because file is large and does not load well in emacs in windows. I'll make it a module.
Ok for the convert.
Arguments for which predicates?