fix split repos when publishing to Sonatype Nexus

Unfortunately the Gradle Publish Plugin behaves erratically in combination with Sonatype Nexus. In particular if timing is bad, split repositories will be created. The only way I could find to mitigate this problem is the `de.marcphilipp.nexus-publish` plugin, which will create a Sonatype repository in a pre-step, then publish all artifacts to this repository. As far as I could see it works fine for releases and snapshots, has a shorter config and solves the problem at hand. Also compare gradle/gradle#5711

Signed-off-by: Peter Gafert <[email protected]>

prepare release `0.14.0`

Consistently set version to `0.14.0` in user guide by using an attribute reference to `{revnumber}`. Also upgraded dependencies of AsciiDoctor to current versions and included `/docs` into the core build, so attributes like the version are automatically consistent and we have a task in the root project to create the user guide.

Signed-off-by: Peter Gafert <[email protected]>

create release news for `0.13.1`

Signed-off-by: Peter Gafert <[email protected]>

prepare release 0.13.0

Signed-off-by: Peter Gafert <[email protected]>

Create release news article

Signed-off-by: Peter Gafert <[email protected]>

Automate release artifact checks:

- POM correct?
- Manifest correct?
- Thirdparty repackaged?
- Sources uploaded?
- Javadoc uploaded?

Signed-off-by: Peter Gafert <[email protected]>

prepare release 0.10.2

Signed-off-by: Peter Gafert <[email protected]>

prepare release 0.10.2

Signed-off-by: Peter Gafert <[email protected]>

Update versions for new release 0.10.1

Signed-off-by: Peter Gafert <[email protected]>

Prepare release 0.10.0

Signed-off-by: Peter Gafert <[email protected]>