[maven-release-plugin] prepare release jenkins-1.534
[maven-release-plugin] prepare for next development iteration
updated changelog for release
updated changelog as a part of the release
merged back the RC branch

Conflicts:
	maven-plugin/pom.xml
	plugins/pom.xml
	ui-samples-plugin/pom.xml
Merge branch 'master' of github.com:jenkinsci/jenkins