Release date and prerelease warning should be generated

[jni]

Currently at the start of the release notes we have a header with the date and
a warning message if we are still in pre-release stage. These are added
manually by the release manager, but they could/should be generated
automatically based on the tag (does it have an alpha/beta/rc tag).

[Czaki]

Do you mean on the release page or in the release file? When in file, then will be no file generation on tag, but always it will be some dev.

[jni]

On the release page. These lines:

89fff84 (#8)