Publish maven artifact containing shaded sources

When working against the shaded dependencies it is not possible to jump to the source of a class, since we don't build source jars.

The source jars can be created by adding the following lines to the maven-shade-plugin configuration:
```
true
true
```

This is mostly blocked by legal questions:
* Do we have to modify the release process for these jars?
* Do we have to vote on the shaded source release?
* Do we have to modify NOTICE/LICENSE files?
* Are we allowed to publish a sources jar that isn't actually the source of the project?
* Are we allowed to publish a sources jar that not necessarily can be compiled to the binary?
* If the shaded source and binary are the result of 2 separate shading processes we can't guarantee it.