11607 scripts

This is a follow on to gh-1324.

 * ~~Matlab files (`.m`) have been added though no example script is yet available.~~ (See http://github.com/openmicroscopy/omero-user-scripts)
 * An extension point has been added to allow using alternative `jython`, `python`, and `matlab` launchers.
```
bin/omero config set omero.launcher.python /opt/virtualenv/bin/python2.7
```

/cc @sbesson @ctrueden


See also:
 * openmicroscopy/ome-documentation#554
 * ome/scripts#54
 * openmicroscopy/omero-example-scripts#3
 * https://github.com/ome/scripts (description and URL updated)


Testing:
 * Copy [jy_example.py](https://github.com/joshmoore/omero-user-scripts/blob/master/jy_example.jy) into your lib/scripts directory (or clone the repo)
 * Check that `bin/omero script list` shows the jy file.
 * Use `bin/omero script launch` to launch it.
 * Run `bin/omero script disable`
 * It should disappear from `list`
 * Re-enable it with `bin/omero script enable`.