Improved the self-documentation.

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Code refactoring

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>
Merge branch 'master' of https://github.com/jenkinsci/ownership-plugin

Conflicts:
	src/main/java/com/synopsys/arc/jenkins/plugins/ownership/OwnershipDescription.java
	src/main/java/com/synopsys/arc/jenkins/plugins/ownership/OwnershipPlugin.java
	src/main/java/com/synopsys/arc/jenkins/plugins/ownership/jobs/OwnershipItemListener.java
Fixed the handling of missing co-owners, which may be passed as null.

Signed-off-by: Oleg Nenashev <o.v.nenashev@gmail.com>