Update plugins to latest revisions

This change bumps up the API version to 2.8 in the pom.xml files
of the plugins:

- commit message length checker
- cookbook
- replication
- reviewnotes

Change-Id: I1842daaf89a4484a0cab713a6ef45af0c772d5b7
Set version to 2.8

Set the version to 2.8 in the VERSION file and in the plugin
archetypes' pom files.

Change-Id: I47f95e8786645ef29e31383cac97f70232882ee1