Document how to publish OSGi bundles

[raboof]

In Akka, we publish OSGi bundles by replacing the packageBin task:

   Compile / packageBin := OsgiKeys.bundle.value

The advantage is that this way the bundle will be picked up correctly by other plugins publishing the packaged artifacts.

A nonobvious effect of this approach is that this will render customizations of the packageBin task, such as changing Compile / packageBin / mappings, ineffective.

Do we want to document/encourage publishing packages like this? Are there alternative solutions? If we recommend this, should we try to be as faithful as possible to the default packageBin behavior and try to honour the mappings?