Additional functionality for the Git module.

Added functionality to reset a release train which actively resets to the latest state of the remote branch. Added functionality to push changes to the remote server and push tags individually. Added functionality to create commits for modules.

Release operations now create two commits for the changelog update and the pom modifications. Release conclude does so for the preparation of the next development iteration.

Added git.author infrastructure property to make sure we use a real user for the git commits.