EnvAction to support hierarchical jobs (cloudbees folders)
ItemGroup is not fine-grained enough to detect folder
module-based jobs also implement ItemGroup
so have to use 'instance of Job'
use relative path
use fullName if source is explicitly configured with absolute path
better handle backward relative and absolute path
handle "/" for jenkins root
handle ".." for parent ItemGroup
manage relative job name when considering renamed items
Merge branch 'folders'
Merge branch 'rename'

Conflicts:
	src/main/java/hudson/plugins/copyartifact/CopyArtifact.java