All test pass, except for the TestConfig suite, which is not too critical as the
plan for this version onwards is to avoid configuration as much as possible.
* Removed old/unnecessary models
* Added a `simulation.{iter_}from_py` method to load simulations from python
files
* Changed tests of examples to run programmatic simulations
* Fixed programmatic examples
* Removed references to `set_state`
* Split some functionality from `agents` into separate files (`fsm` and
`network_agents`)
* Rename `neighboring_agents` to `neighbors`
* Delete some spurious functions
See CHANGELOG.md for a full list of changes
* Removed nxsim
* Refactored `agents.NetworkAgent` and `agents.BaseAgent`
* Refactored exporters
* Added stats to history
