Nodes as Maps

Attempt to render nodes and relationships as 'Castable' maps that
you then can cast to node or rel objects.

Doesn't work yet because of read transactions needed while reading
the lazy result set.

Potential solutions:

1. Require transactions around the whole query + resultset operation
2. Eagerly read the full resultset and convert everything to a real map
3. Start new read-tx for every access to a potential node or rel-object
4. Something better than the 3 above