Add BND manifest generation to the jars

[laeubi]

This adds BND manifest generation to the jars so one could use them inside OSGi.

This currently depends on unreleased features of BND to support multi-release see

• https://github.com/bndtools/bnd/pull/5350

and is also a showcase of how BND might be used to produce a multi.release OSGi bundle.

FYI @stbischof

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