make DataManager::Key having second identity to differentiate pmid_node related actions : use <data_name, NodeId()> as normal data record ; <data_name, pmid_node> for add/remove pmid_node
Merge branch 'vault' of github.com:maidsafe/MaidSafe-Vault into vault

Conflicts:
	src/maidsafe/vault/data_manager/action_add_pmid.cc