Core changes for using the previous build as reference.
Merge remote-tracking branch 'upstream/master'
Including comments from pull request.

Fixing formatting, correcting javadoc.
Changing the order of the buildhistory parameters to match all others.

Add functionality to annotationsaggregator to allow to pass new value
through.
Merge pull request #26 from tom-saunders/master

[JENKINS-13458] Added option to use the previous build as reference.