Redistribute launch scripts in Linux and Mac client zips

Fixes http://trac.openmicroscopy.org/ome/ticket/12340

This PR should fix all the standalone client bundles (OMERO.insight, OMERO.editor and OMERO.importer) for both Linux and Mac OS X platforms:
-  `./build.py release-client` now generates standalone zip bundles for OMERO.editor and OMERO.importer under Linux 
- `OMERO.insight*-{linux,mac}.zip` should only contain the `OMEROinsight_unix.sh` script
- `OMERO.editor*-{linux,mac}.zip` should only contain the `OMEROeditor_unix.sh` script
- `OMERO.importer*-{linux,mac}.zip` should only contain the `OMEROimporter_unix.sh` and `importer-cli` scripts
- Additionally the `OMERO.clients-*{linux,mac}.zip` should still contain all the scripts aboce
- all the Windows clients should be unaffected by this PR

/cc @pwalczysko @bpindelski