JENKINS-17108. This solves the problem with ItemListner.onUpdated not being called if the project was disabled/enabled by pushing the button on the project page. Also solved the problem with ItemListener.onUpdated not getting called if the project description was updated using the edit description on the project page.
Update AbstractItem.java

Should follow this statement:
"Called after a job has its configuration updated."
Update AbstractProject.java

Should follow this statement:
"Called after a job has its configuration updated."
Add changelog for PR #912