Harmonized maven dependency management

This commit harmonizes the dependency management of internal modules
so that versions can be omitted everywhere. Update the maven coordinates
to provide the full groupId for consistency
Fixup POM harmonization

Fix POM harmonization so that the release process now
prepares the dependencies POM rather than starter-parent
Fixup reference guide following dependencies move

Update reference guide to indicate that spring-boot-dependencies should
be imported when not using the parent POM.
Merge pull request #768 from snicoll/module-version-mgt

* module-version-mgt:
  Fixup reference guide following dependencies move
  Fixup POM harmonization
  Harmonized maven dependency management