iteration 4 & last:

iteration 4 & last:

- ForeignNode(s) and ForeignSlice(s) deprecated

- Node and Slice both have a peer_id field that can be used
  for testing locality (peer_is is None)

- associations peer x node and peer x slice not managed in
  a separate table anymore (were peer_node and peer_slice)
  peer_id is defined as a native column instead

- local nodes can be retrieved with
  GetNodes (auth, {'peer_id':None})
  GetNodes (auth, {'hostname':[name1,name2], 'peer_id':None})
or
  GetNodes (auth, None, None, 'local')
  GetNodes (auth, ['name1','name2'] , None, 'local')
- foreign nodes can be retrieved similarly with
  GetNodes (auth, {'hostname':[name1,name2], '~peer_id':None})
or
  GetNodes (auth, ['name1','name2'] , None, 'foreign')

- the 4th argument to GetNodes is named 'scope'.
  It is only experimental by now,  Slices do not have it as of now,
  will decide later whether we provide it for all cached entities

- WARNING :
  Having Nodes and Slices return ALL entities might have impacts on
  other methods; most of which making sense on LOCAL entities only.
  Might need a review.