Fix OSGI exports

[NthPortal]

Fix OSGI exports so scala/jdk classfiles are not removed
from the jar.

Fixes #224.

[NthPortal]

It's not clear to me how the version is bumped - is that just done by tagging for release?

[lrytz]

the module should export scala.jdk only in the 2.11 / 2.12 versions, something like

      OsgiKeys.exportPackage := {
        if (scalaVersion.value.startsWith("2.13."))
          Seq(s"scala.collection.compat.*;version=${version.value}")
        else
          Seq(s"scala.collection.compat.*;version=${version.value},scala.jdk.*;version=${version.value}")
      },

[szeiger]

After further investigation I have to retract my approval. It's still broken in major ways.

The imports in the manifest are wrong. We're currently importing from a SemVer range based on the project's own version. I don't know where this default comes from but it is really bad. Aborting with an error would be a much better default.

We have some code to generate the correct version ranges in Slick: https://github.com/slick/slick/blob/master/project/Osgi.scala

That alone is still not enough though. We have to use different OSGi headers for different Scala versions. Scala 2.13 has a scala.jdk package so we must not export it ourselves on 2.13.

I'll submit my own PR with these fixes.

[NthPortal]

closing in favour of #226