Adjust version check. (rebased onto develop)



This is the same as gh-2226 but rebased onto develop.

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Fix http://trac.openmicroscopy.org.uk/ome/ticket/12045

To test:
 * Open client and try to connect to a 5.1. server e.g. trout. This should not be allowed
 * Try to connect to 5.0.x client: test against gretzky and nightshade