Add --devel option to install the OMERO 5 via Homebrew (rebased onto develop)



This is the same as gh-644 but rebased onto develop.

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This PR fixes an issue reported in https://www.openmicroscopy.org/community/viewtopic.php?f=6&p=13350#p13332

Until we archive the OMERO 4.4 Homebrew formula, the OMERO 5 formula needs be installed by passing the `--devel` option (see http://ci.openmicroscopy.org/job/OME-5.0-merge-homebrew/).