MRM-907 - Remove VersionedReference/ProjectReference/ArtifactReference from RepositoryProxyConnectors

* Metadata proxy fetching has been refactored from two methods to one single method.
* Artifacts, metadata and resources are now written to a temporary working area. Post download policies are run before the proxied data are put in the repository proper. 



git-svn-id: https://svn.apache.org/repos/asf/archiva/branches/metadata-rejig-1.2@685399 13f79535-47bb-0310-9956-ffa450edef68
9 files changed