Updated example scripts to the new API.

Also added new example network_array_2d.py.
network_array_2d.py is similar to the 2drepresentation.py example
except it uses a Network Array in place of an ensemble. Supposed to
demonstrate the most basic use of Network Arrays.

Note:
- All network/ensemble/node names need to be capitalized
- Comments are aligned to each other
- Uses model.build()
- Currently assuming that functions passed to make_node take time as an
  input, but this is subject to change over to Terry's generator scheme

Todo:
- Add header, and maybe get rid of big transform comment