Bugfixes

Detect the CC2538 and include the Z-Stack build in the device model string (a571726, #72).
Properly handle older Z-Stack SYS.SetTxPower responses (#82)
Permit deserialization failures with the undocumented ZDO.ParentAnnceRsp command (aaf0c31, home-assistant/core#50005).
Silence "Unhandled command" warnings for ZDO.ParentAnnceRsp, ZDO.ConcentratorInd, and ZDO.MgmtNWKUpdateNotify (#75).
Joins through specific routers will not also open the coordinator for joining on Z-Stack 20210708 (properly fixes #53)

New features

Treat messages from unknown devices as implicit joins. This allows for existing networks to be mapped out without explicitly re-joining most devices (#73)
Normalize command logging for NVRAM reads and writes (0adeb9b)