Terminology section restructuring

Currently, we have a big terminology section that tries to describe most
parts of SHACL from start.

However, we have dedicated sections for most of the terms introduced in the
terminology, e.g. shapes, targets, filters, constraints, validation, etc
and there is some repetition in some definition and backwards references to
the terminology section through respec

I suggest we keep the basic terminology (e.g. from "Basic RDF Terminology"
until "SHACL Instance") and try to integrate the rest in the spec.

Any ideas, comments?

Best,
Dimitris
-- 
Dimitris Kontokostas
Department of Computer Science, University of Leipzig & DBpedia Association
Projects: http://dbpedia.org, http://rdfunit.aksw.org,
http://aligned-project.eu
Homepage: http://aksw.org/DimitrisKontokostas
Research Group: AKSW/KILT http://aksw.org/Groups/KILT