Prepare for release of version 2.8.3.

Bump version to 2.8.2.

updated ChangeLog for 2.8.1

Prepare version 2.8.0.

Prepare for 2.7.0 release.

new release

Added tag 2.6.2 for changeset f70cc626f740

Added tag 2.6.1 for changeset 869264aaa293

Added tag 2.6.0 for changeset 9203d309072e

Added tag 2.5.6 for changeset b8896f4b2e08