Scripts menu 11434

Scripts menu should handle multiple levels (not just 2 as before).
This allows more flexibility for others to add their scripts without name conflicts. See https://trac.openmicroscopy.org.uk/ome/ticket/11434

To test:
 - With the standard scripts that ship with OMERO, you should only see two levels, with each level exposed by clicking on the directory. Clicking 'BACK' should return you to the previous directory.

![screen shot 2013-09-09 at 11 38 08](https://f.cloud.github.com/assets/900055/1106230/be503800-193d-11e3-8812-f9d4f0f33db6.png)
![screen shot 2013-09-09 at 11 38 48](https://f.cloud.github.com/assets/900055/1106231/c15d0456-193d-11e3-89fa-4496e796be88.png)

 - Try adding a script - You can add existing scripts with a different path (to appear like new scripts) by simply starting from a different dir to upload. For example:

```
$ omero script upload components/tools/OmeroPy/scripts/omero/analysis_scripts/Kymograph.py --official
$ cd components/tools/
$ omero script upload OmeroPy/scripts/omero/analysis_scripts/Kymograph.py --official
```

Now you'll have a couple more top-level directories, and the 'official' ones will be under "OMERO".

![screen shot 2013-09-09 at 11 43 18](https://f.cloud.github.com/assets/900055/1106247/3eddc83e-193e-11e3-9e04-d52a5959f8f2.png)

![screen shot 2013-09-09 at 11 43 33](https://f.cloud.github.com/assets/900055/1106248/436ec588-193e-11e3-80e2-47ee1f67e58e.png)