Robot structure web (rebased onto develop)



This is the same as gh-1650 but rebased onto develop.

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This is the web additions to the Robot testing framework. Web tests are currently failing, and should be fixed before this PR is merged. This was originally opened by JM: https://github.com/openmicroscopy/openmicroscopy/pull/1639

Build should pass at http://hudson.openmicroscopy.org.uk/view/Failing/job/OMERO-merge-robotframework-stable/