[Sculptor 3] Preparations for the release finished - ready for official announcement and switch to new forum

[Torsten Juergeleit]

All preparations finished:

* Sculptor version on homepage updated to 3.0.0

* New forum prepared and old forum links updated

* What's new page updated for version 3.0.0

* Link to external blog changed to internal blog

* Blog post for release of version 3.0.0 created

* Sculptors Maven plugin is available on Maven Central

So we're ready for an official announcement.

@Pavel, please create an announcement post for the release of Sculptor 3.0.0 in the new forum.

And in the old forum please create a post for inviting the members of the old forum to join the new forum.

/Torsten