Add "dead" network resource states to API models

`pynsot.models.Network` sets `state: assigned` for host addresses and `state: allocated` otherwise. Don't personally have a use-case for setting to `oraphaned` or `reserved` (NSoT docs also don't delve into states much), but we should add this in for parity.

Implementation could be an `.archive()` method or just `.orphan()` and `.reserve()`.

Not critical, but wanted it to be documented.