Redirect --devel versions of OMERO and Bio-Formats formulas

For simplicity, the following commands
```
brew install bioformats --devel
brew install omero --devel
```
now point at the latest tag of OMERO and Bio-Formats on the develop branch rather than building the tip of this branch. In terms of infrastructure, OMERO-homebrew-stable and OMERO-homebrew-develop jobs should now test the full installation of the last tagged versions on the stable and develop branch respectively.

This PR also fixes various warnings returning by `brew audit`.