DATAMONGO-859 - Prepare release 1.5 M1.

Prepare issue branch.
DATAMONGO-859 - Prepare release 1.5 M1.

Updated readme.md and mongodb.xml to reflect recent version. Updated Spring Data Commons and Spring Data Build versions in pom.xml. Update pom.xml to use release repository. Updated docbkx to use recent Spring Data Commons version. Updated changelog to reflect changes and releases.

Original pull request: #161.