Add module support & query their information during update cycle (#243)

* Add module support & modularize existing query

This creates a base to expose more features on the supported devices.
At the moment, the most visible change is that each update cycle gets information from all available modules:
* Basic system info
* Cloud (new)
* Countdown (new)
* Antitheft (new)
* Schedule (new)
* Time (existing, implements the time/timezone handling)
* Emeter (existing, partially separated from smartdevice)

* Fix imports

* Fix linting

* Use device host instead of alias in module repr

* Add property to list available modules, print them in cli state report

* usage: fix the get_realtime query

* separate usage from schedule to avoid multi-inheritance

* Fix module querying

* Add is_supported property to modules

kasa/modules/countdown.py

@@ -0,0 +1,6 @@
+"""Implementation for the countdown timer."""
+from .rulemodule import RuleModule
+
+
+class Countdown(RuleModule):
+    """Implementation of countdown module."""