#318 Added script to sync Turtle & JSON-LD snippets

[bergos]

• Adds a script to verify if the Turtle and JSON-LD code snippets are in sync and generates JSON-LD for missing or out-of-sync code snippets.
• Adds/updates JSON-LD snippets in Core and SPARQL according to the sync script.
• Adds OWL namespaces to Core and SPARQL. The namespace is used only in the SPARQL specification, but I wanted to keep the list in sync to simplify the automatic processing.
• Makes minor changes to some Turtle examples to make them parsable and aligns namespaces in the examples with the defined list.
• Adds JavaScript and CSS for multi-format snippet support to the SHACL SPARQL spec.
• Some examples have been processed manually because of bugs or missing features in RDF/JS libraries. There are comments next to the entries in the ignore list.
• Changes for Core and SPARQL specifications are in different commits to make them easier to review.

Closes #318

• See the SHACL Core document rendered online here
• See the SHACL SPARQL document rendered online here