DATAGRAPH-359 - Prepare 2.3 M1 release.

Updated changelog: pull in changelog for 2.2.1 release. Consistent ticket reference formatting. Moved changelog etc. to correct place to be picked up for distribution. Upgraded to Spring Data Parent 1.1.0.RELEASE, Spring Data Commons 1.6.0.M1. Switched to milestone repository. Upgraded to APT plugin as defined in parent pom.