Adding KGCL support via kgcl-rdflib

[cmungall]

This PR adds experimental support for KGCL, making use of the kgcl-rdflib library by @ckindermann @jamesaoverton @hrshdhgd

Currently support is most complete for the rdflib backend, with some partial support for sqlite, funowl and pronto. Note that currently rdflib is quite slow to parse large ontologies.

KGCL commands are passed by the apply command:

runoak -i go.owl.ttl apply "rename 'nucleus' to 'foo'" -o go-modified.owl.ttl -O ttl

You can get back summaries using diff:

runoak -i go.owl.ttl -vv diff -X go-modified.owl.ttl

• Adding bindings for kgcl-rdflib
• recognizing ofn suffix and rdflib prefix
• Adding some preliminary KGCL bindings. These may move to another package - see Consider adding kgcl bindings althonos/pronto#180
• fixing signature
• adding skos definition
• Adding an apply command for applying KGCL patches Adding a KGCL diff Rationalizing other commands
• Implementing diffs by wrapping kgcl-rdflib