DATAMONGO-853 - Update does not allow null keys anymore.

Added check for blank / null keys when adding key to Update.

Original pull request: #129.
DATAMONGO-856 - Documentation updates.

Updated references from springsource.org to spring.io. Updated references to mongodb.org. Update vendor to Pivotal Software, Inc. Update required/recommended versions. Update CustomConversions configuration section. Added missing section id's. Fixed some typos. Added missing JavaDoc.

Original pull request: #128.
DATAMONGO-856 - Documentation update.

Removed outdated why-spring-data-doc. Removed CouchDB reference from requirements document. Fixed some typos. Added missing opening <para>-element. Fixed rendering of author information. Added copyright and product name information.

Original pull request: #128.
DATAMONGO-854 - Prepare 1.4.0.RELEASE.

Update artifact version in readme for release and snapshot.
Use commons 1.7.0 resources in docbkx.
Update changelog.
Update version information in notice and readme.

Original pull request: #130.
DATAMONGO-854 - Release version 1.4.0 RELEASE.
DATAMONGO-854 - Prepare next development iteration.
Upgrade the versions of various dependencies
Upgrade versions of various dependencies