Fix demo jcb links

[will-moore]

This fixes broken image rendering links at http://figure.openmicroscopy.org/demo/#file/1 by updating to use images at https://omero.lifesci.dundee.ac.uk/webclient/?show=dataset-65051

To test locally:

• Checkout this branch, then:

  $ grunt demo
  $ cd demo
  $ python -m SimpleHTTPServer

• open http://localhost:8000/#file/1

NB: This doesn't fix links for other demo files. 2 -> 5

[will-moore]

These changes were ported over to https://github.com/ome/omero-figure/pull/327 and merged.