Revert "HACK: add actual output comparisons"

This reverts commit d4496b3527cdec0a309d009d5e1f7e54ab5c897f.

Conflicts:
	test/nengo_tests/test_array.py
fix bugs introduced in revert
remove old way of extracting ensemble origin data

- ref #17
- use just probes to collect ensemble origin data
- keep the old interface for client accessing of probe data
- probe objects keep a reference to network and get data from it when requested