[FIXED JENKINS-7798]

File size should be shown on project dashboard for archived artifacts.

Run.java:
	Add member String length to Artifact object.
	Add paramter String len to Artifact constructor.
	Add method String getLength to Artifact object.
	addArtifacts method of Run class gets length of files as string
	for actual files or "0" if a directory and passes this as arg
	to Artifact constructor.

artifacts-index.jelly and artifactList.jelly
	reworked to use same approach as
	core/src/main/resources/hudson/model/DirectoryBrowserSupport/dir.jelly
	The desire being a consistent look in the interface.

Signed-off-by: Stephen Ware <stephen.e.ware@intel.com>