Feature: Add shareable URL capturing the app state

[jaw111]

Requirement: Allow users to easily share links to a certain application state

The relevant values should be somehow represented in the URL:

• RDF input text
• RDF input media type
• SPARQL query text
• SPARQL query results media type

Seems logical to represent these in the URL as query string parameters, either by just adding the (suitably URL encoded) values, or use data URLs to allow also representing the media type (and possibly base64 encoding the value).