Enable content negotation from the lod-view

[gb-beng]

Comment about this that was part of the code (moving that to here now):

# TODO: add the parameter 'format' so that a return format can also be added as parameter to the URL,
# instead of only allowing content negotiation by the accept http header. The rationale is that we
# can't send a request from the lod-view with an accept header. It just isn't possible.
# The should not be shown when the json-ld, etc. formatted data is shown in the browser. It should list the
# resource URI only. Still a coolURI

Alternatively we can consider using JavaScript (fetch or XMLHttpRequest).