Improvement navigate and check proxy attribute

```
I defined in a class the following
<class name="LoteServicio" table="LotesServicios" proxy="ILoteServicio">

The plugin does not check if ILoteServicio exists and does not navigate to
it...

I don't know how difficult it is, but it will be nice to have this check also.
```

Original issue reported on code.google.com by `gustavo.ringel@gmail.com` on 12 Oct 2008 at 7:07
