Revision 219276

Resolving: MNG-397

o Added ResolutionGroup class which contains a set of artifacts and a list of repositories to resolve them.
o Made the ResolutionNode a standalone class, and added the remote repositories to it
o Changed ArtifactMetadataSource.retrieve(..) to return ResolutionGroup rather than Set, in order to help keep track of the repositories which should be used to resolve the retrieved artifacts.

We need some tests for this...