OMERO.matlab agent

This trivial PR sets the agent to `OMERO.matlab` instead of the default `OMERO.java` when initializing a client using `connectOmero`.

Since there is no property to read the `__agent` value in the client, to test this PR, create a client/session from MATLAB using `loadOmero()` and check the agent is correctly in `Blitz-0.log`  e.g.

```
2014-05-04 02:01:29,185 INFO  [ ome.services.blitz.fire.SessionManagerI] (l.Server-4) Created session ServiceFactoryI(session-1ebd489e-8e1f-49c6-9d57-e6f5fa1c5097/183b2b5d-5af7-44b7-9edd-a190eaba511d) for user user-1 (agent=OMERO.matlab)
```