Removing dependency on rdfextras

I copied rdfextras.utils.cmdlineutils to rdfextras_web/cmdlineutils.py
and fixed the imports as well as some other problems.
Use cmdlineutils from rdflib.extras
Require rdflib>=4.0
Merge pull request #2 from uholzer/no-rdfextras

Removing dependency on rdfextras
import rdfs2dot, rdf2dot - time endpoint as well, register namespaces once and for lod as well
and fixed some bugs with menu, added caching + showing types of linked things
fixed doing all the work for not-rendering the index page
cache fix
added crappy search + class navigation for isntances
keep namespace-prefixes for individual resource graphs
server-deployment based testing...
merged