Robot framework: add CLI plugin to generate configuration file

In preparation of the reactivation of the Robot framework jobs in our daily workflow, this PR adds modification allowing these tests to be run against an existing deployed CI integration servers.

A new  CLI plugin is created within the `components/tests/ui` folder wich a `config` subcommand which can generate Robot configuration file from a template stored in `etc`, the OMERO.web settings and the `ice.config` file. The command should read as:

```
dist/bin/omero --path components/tests/ui/plugins robot config > components/tests/ui/config.txt
```

The user/password to use for tests can be changed by using the `ICE_CONFIG` environment variable to any `ice.config` file on the system.

This PR should be tested:
- locally against a development server to verify the configuration is not broken
- on the CI infrastructure to test the web prefix logic is supported.

Note this PR does not fix currently failing Web tests. These will be fixed once the job is reactivated.

/cc @will-moore @jburel @aleksandra-tarkowska