XD-2061 Add Redis sink module

 - Add Redis sink with the following options:
    - topic (a SpEL expression)
    - hostname, port and password
Sorry, I may not have made myself clear.
What I mean is:
In modules.yml:
```
sink.redis.key: 'foo'
```

`module info` at the shell should show `'foo'` as the (default) value of `keyExpression` (as well as `foo` for the default of `key`)