Add support for peer-to-peer associations within the imported content set

[pmonks]

Migrated from https://code.google.com/p/alfresco-bulk-filesystem-import/issues/detail?id=10

Add support for peer-to-peer associations within the imported content set. Will require a two-pass process (first pass loads all the content, second pass wires up the peer-to-peer associations between those content items).