[maven-release-plugin] copy for tag 2.12

[maven-release-plugin] copy for tag 2.10.4

[maven-release-plugin] copy for tag 2.10.3

[maven-release-plugin] copy for tag 2.10.2

[maven-release-plugin] copy for tag 2.11

[maven-release-plugin] copy for tag 2.10.1

[maven-release-plugin] copy for tag 2.10

2.9.1 release preparation: version updated in poms

Added Release Highlights to Migration Guide.

Change-Id: Ib031ada0e02781c43850ad1efd3e42c94ac59d5e
Signed-off-by: Michal Gajdos <michal.gajdos@oracle.com>

[maven-release-plugin] copy for tag 2.8