Prepare maven release

[dhuebner]

deploy a release build to maven central.
Workflow:

• create branch named 'release_x.y.z'
• update versions
• push the branch
• Jenkins will trigger a build and publish to maven staging
• review and publish staging repo from sonatype web UI

[cdietrich]

nice. will there be a release update site at eclipse too?

[dhuebner]

@cdietrich Yes, as soon as wir prepared a p2 release. This was a maven warm-up

[dhuebner]

A readme will be available here:

https://github.com/eclipse/Xpect/tree/master/org.eclipse.xpect.releng/README.md

[cdietrich]

the current maven artifacts dont have dependencies, thus the user has to make sure the relevant ones are present themselves